Chemical Constituents of Propolis from Vietnamese Trigona minor and Their Antiausterity Activity against the PANC-1 Human Pancreatic Cancer Cell Line

Exploring the Functional Properties of Propolis, Geopropolis, and Cerumen, with a Special Emphasis on Their Antimicrobial Effects

Bee propolis has been touted as a natural antimicrobial agent with the potential to replace antibiotics. Numerous reports and reviews have highlighted the functionalities and applications of the natural compound. Despite much clamor for the downstream application of propolis, there remain many grounds to cover, especially in the upstream production, and factors affecting the quality of the propolis. Moreover, geopropolis and cerumen, akin to propolis, hold promise for diverse human applications, yet their benefits and intricate manufacturing processes remain subjects of intensive research. Specialized cement bees are pivotal in gathering and transporting plant resins from suitable sources to their nests. Contrary to common belief, these resins are directly applied within the hive, smoothed out by cement bees, and blended with beeswax and trace components to create raw propolis. Beekeepers subsequently harvest and perform the extraction of the raw propolis to form the final propolis extract that is sold on the market. As a result of the production process, intrinsic and extrinsic factors, such as botanical origins, bee species, and the extraction process, have a direct impact on the quality of the final propolis extract. Towards the end of this paper, a section is dedicated to highlighting the antimicrobial potency of propolis extract.

Antimicrobial, Cytotoxic, and α-Glucosidase Inhibitory Activities of Ethanol Extract and Chemical Constituents Isolated from Homotrigona apicalis Propolis-In Vitro and Molecular Docking Studies

The chemical investigation of Homotrigona apicalis propolis collected in Binh Dinh province, Vietnam, led to the isolation of nine compounds, including four sesquiterpenes: spathulenol (1), 1αH,5βH-aromandendrane-4β,10α-diol (2), 1β,6α-dihydroxy-4(15)-eudesmene (3), and 1βH,5βH-aromandendrane-4α,10β-diol (4); three triterpenes: acetyl oleanolic acid (5), 3α-hydroxytirucalla-8,24-dien-21-oic acid (6), and ursolic acid (7); and two xanthones: cochinchinone A (8) and α-mangostin (9). Sesquiterpens 1-4 and triterpene 6 were isolated for the first time from stingless bee propolis. Plants in the Cratoxylum and Aglaia genus were suggested as resin sources of the propolis sample. In the antibacterial activity evaluation, the EtOH extract only showed moderate activity on S. aureus, while the isolated compounds 7-9 showed good antibacterial activity, with IC50 values of 0.56 to 17.33 µg/mL. The EtOH extract displayed selective cytotoxicity against the A-549 cancer cell line, with IC50 values of 22.82 ± 0.86 µg/mL, and the xanthones 8 and 9 exhibited good activity against the KB, HepG-2, and A-549 cancer cell lines, with IC50 values ranging from 7.55 ± 0.25 µg/mL to 29.27 ± 2.07 µg/mL. The cytotoxic effects of xanthones 8 and 9 were determined by the inhibition of the EGFR and HER2 pathways using a molecular docking study. Compounds 8 and 9 displayed strong binding affinity with EFGR and HER2, with values of -9.3 to -9.9 kcal/mol. Compounds 5, 8, and 9 showed potential α-glucosidase inhibitory activities, which were further confirmed by computational studies. The binding energies of compounds 5, 8, and 9 were lower than that of arcabose.

Chemodiversity of propolis samples collected in various areas of Benin and Congo: Chromatographic profiling and chemical characterization guided by 13 C NMR dereplication

INTRODUCTION

Propolis is a resinous natural substance collected by honeybees from buds and exudates of various trees and plants; it is widely accepted that the composition of propolis depends on the phytogeographic characteristics of the site of collection.

OBJECTIVES

The aim of this study was to determine the phytochemical composition of ethanolic extracts from eight propolis batches collected in different regions of Benin (north, center, and south) and Congo, Africa.

MATERIAL AND METHODS

Characterization of propolis samples was performed by using different hyphenated chromatographic methods combined with carbon-13 nuclear magnetic resonance (¹³ C NMR) dereplication with MixONat software. Their antioxidant or anti-advanced glycation end-product (anti-AGE) activity was then evaluated by using diphenylpicrylhydrazyl and bovine serum albumin assays, respectively.

RESULTS

Chromatographic analyses combined with ¹³ C NMR dereplication showed that two samples from the center of Benin exhibited, in addition to a huge amount of pentacyclic triterpenes, methoxylated stilbenoids or phenanthrenoids, responsible for the antioxidant activity of the extract for the first one. Among them, combretastatins might be cytotoxic. For the second one, the prenylated flavanones known in Macaranga-type propolis were responsible for its significant anti-AGE activity. The sample from Congo was composed of many triterpene derivatives belonging to Mangifera indica species.

CONCLUSION

Therefore, propolis from the center of Benin seems to be of particular interest, due to its antioxidant and anti-AGE properties. Nevertheless, as standardization of propolis is difficult in tropical zones due to its great chemodiversity, a systematic phytochemical analysis is required before promoting the use of propolis in food and health products in Africa.

Propolis: A Detailed Insight of Its Anticancer Molecular Mechanisms

Cancer is the second most life-threatening disease and has become a global health and economic problem worldwide. Due to the multifactorial nature of cancer, its pathophysiology is not completely understood so far, which makes it hard to treat. The current therapeutic strategies for cancer lack the efficacy due to the emergence of drug resistance and the toxic side effects associated with the treatment. Therefore, the search for more efficient and less toxic cancer treatment strategies is still at the forefront of current research. Propolis is a mixture of resinous compounds containing beeswax and partially digested exudates from plants leaves and buds. Its chemical composition varies widely depending on the bee species, geographic location, plant species, and weather conditions. Since ancient times, propolis has been used in many conditions and aliments for its healing properties. Propolis has well-known therapeutic actions including antioxidative, antimicrobial, anti-inflammatory, and anticancer properties. In recent years, extensive in vitro and in vivo studies have suggested that propolis possesses properties against several types of cancers. The present review highlights the recent progress made on the molecular targets and signaling pathways involved in the anticancer activities of propolis. Propolis exerts anticancer effects primarily by inhibiting cancer cell proliferation, inducing apoptosis through regulating various signaling pathways and arresting the tumor cell cycle, inducing autophagy, epigenetic modulations, and further inhibiting the invasion and metastasis of tumors. Propolis targets numerous signaling pathways associated with cancer therapy, including pathways mediated by p53, β-catenin, ERK1/2, MAPK, and NF-κB. Possible synergistic actions of a combination therapy of propolis with existing chemotherapies are also discussed in this review. Overall, propolis, by acting on diverse mechanisms simultaneously, can be considered to be a promising, multi-targeting, multi-pathways anticancer agent for the treatment of various types of cancers.

The Role of Propolis as a Natural Product with Potential Gastric Cancer Treatment Properties: A Systematic Review

Gastric cancer is one of the most common, aggressive, and invasive types of malignant neoplasia. It ranks fifth for incidence and fourth for prevalence worldwide. Products of natural origin, such as propolis, have been assessed for use as new complementary therapies to combat cancer. Propolis is a bee product with antiproliferative and anticancer properties. The concentrations and types of secondary metabolites contained in propolis mainly vary according to the geographical region, the season of the year, and the species of bees that make it. The present study is a systematic review of the main articles related to the effects of propolis against gastric cancer published between 2011 and 2021 in the PubMed and Science Direct databases. Of 1305 articles published, only eight studies were selected; among their principal characteristics was the use of in vitro analysis with cell lines from gastric adenocarcinoma and in vivo murine models of the application of propolis treatments. These studies suggest that propolis arrests the cell cycle and inhibits proliferation, prevents the release of oxidizing agents, and promotes apoptosis. In vivo assays showed that propolis decreased the number of tumors by regulating the cell cycle and the expression of proteins related to apoptosis.

The therapeutic potential of natural products for treating pancreatic cancer

Pancreatic cancer is one of the most malignant tumors of the digestive tract, with the poor prognosis and low 5-year survival rate less than 10%. Although surgical resection and chemotherapy as gemcitabine (first-line treatment) has been applied to the pancreatic cancer patients, the overall survival rates of pancreatic cancer are quite low due to drug resistance. Therefore, it is of urgent need to develop alternative strategies for its treatment. In this review, we summarized the major herbal drugs and metabolites, including curcumin, triptolide, Panax Notoginseng Saponins and their metabolites etc. These compounds with antioxidant, anti-angiogenic and anti-metastatic activities can inhibit the progression and metastasis of pancreatic cancer. Expecting to provide comprehensive information of potential natural products, our review provides valuable information and strategies for pancreatic cancer treatment.

Antineoplastic and Antitrypanosomal Properties of Propolis from Tetragonula biroi Friese

Propolis, popularly known as bee glue, is a resinous, sticky substance produced by different bee species across the globe. Studies on the biological properties of propolis from the Philippines are rare. Hence, the current study aims at the chemical characterization of propolis produced by the stingless bees Tetragonula biroi Friese from the Philippines and to investigate its antitrypanosomal and anticancer properties. The determination of the chemical composition and characterization of propolis samples was achieved using liquid chromatography-mass spectrometry (LC-MS), -high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD), and nuclear magnetic resonance (NMR) spectroscopy. Three major triterpenes were isolated and identified using HRESI-MS and 1H/13C NMR techniques. The spectral studies confirmed the presence of compounds such as isomangiferolic acid, 27-hydoxymangiferonic acid, and 27-hydroxyisomangiferolic acid. All crude propolis samples, isolated fractions, and pure compounds demonstrated moderate antitrypanosomal and anticancer properties compared to control drugs. Amongst the tested compounds, 27-hydoxymangiferonic acid exhibited the highest antitrypanosomal activity at a concentration of 11.6 µg/mL. The highest anticancer effect was demonstrated by the Ph-2 fraction, followed by 27-hydroxyisomangiferolic acid, with IC50 values of 129.6 and 153.3 µg/mL. Thus, it can be concluded that the observed biological activity of Philippine propolis is due to the combinatorial effect or synergistic action of the active compounds 27-hydoxymangiferonic acid and 27-hydroxyisomangiferolic acid.

Antifungal–antiproliferative norcycloartane-type triterpenes from the Red Sea green alga Tydemania expeditionis

The current work aims to isolate the bioactive secondary metabolites from the Red Sea green alga T. expeditionis. Its organic extract was partitioned and analyzed using chromatographic and spectroscopic techniques. Four triterpenoids of the cycloartane-carbon skeleton were identified as: 29-norcycloartane-3-en-23,28-diol (1), 29-norcycloartane-5,24-dien-3-ol-23-one (2), 29-norcycloartane-3,24-dien-3-ol-23-one (3), and 29-norcycloartane-5,24-dien-3-ol (4), along with hydroxylated C-18 fatty acid, 3-hydroxyoctadeca-15(Z)-enoic acid (5). The antiproliferative activity of the isolated metabolites was examined against three cancer cell lines, i.e., HeLa, HepG-2, and MCF-7. Compounds 2 and 3 demonstrated a strong antiproliferative effect against all cells with IC50 values ranging from 17.8 ± 1.71 to 23.3 ± 1.66 µM. Compounds 1 and 4 showed a moderate antiproliferative effect against all cell lines with IC50 values ranging from 44.7 ± 2.32 to 65.0 ± 3.66 µM. The antifungal activity of all compounds has been tested against several fungi. Compounds 2–4 revealed strong inhibition against A. flavus and Fusarium oxysporum. Compounds 1–4 showed moderate to weak inhibition activity against A. niger, A. fumigatus, C. albicans, and C. tropicalis. Compound 5 showed weak to non-detected activity against all cell lines and microbes. The results indicated that norcycloartanes exhibit antiproliferative and antifungal activities, especially those with α,β-unsaturated ketones in their side chain.

Propolis: An update on its chemistry and pharmacological applications

Propolis, a resinous substance produced by honeybees from various plant sources, has been used for thousands of years in traditional medicine for several purposes all over the world. The precise composition of propolis varies according to plant source, seasons harvesting, geography, type of bee flora, climate changes, and honeybee species at the site of collection. This apiary product has broad clinical applications such as antioxidant, anti-inflammatory, antimicrobial, anticancer, analgesic, antidepressant, and anxiolytic as well asimmunomodulatory effects. It is also well known from traditional uses in treating purulent disorders, improving the wound healing, and alleviating many of the related discomforts. Even if its use was already widespread since ancient times, after the First and Second World War, it has grown even more as well as the studies to identify its chemical and pharmacological features, allowing to discriminate the qualities of propolis in terms of the chemical profile and relative biological activity based on the geographic place of origin. Recently, several in vitro and in vivo studies have been carried out and new insights into the pharmaceutical prospects of this bee product in the management of different disorders, have been highlighted. Specifically, the available literature confirms the efficacy of propolis and its bioactive compounds in the reduction of cancer progression, inhibition of bacterial and viral infections as well as mitigation of parasitic-related symptoms, paving the way to the use of propolis as an alternative approach to improve the human health. However, a more conscious use of propolis in terms of standardized extracts as well as new clinical studies are needed to substantiate these health claims.

Computational Study of Asian Propolis Compounds as Potential Anti-Type 2 Diabetes Mellitus Agents by Using Inverse Virtual Screening with the DIA-DB Web Server, Tanimoto Similarity Analysis, and Molecular Dynamic Simulation

Propolis contains a wide range of pharmacological activities because of their various bioactive compounds. The beneficial effect of propolis is interesting for treating type-2 diabetes mellitus (T2DM) owing to dysregulation of multiple metabolic processes. In this study, 275 of 658 Asian propolis compounds were evaluated as potential anti-T2DM agents using the DIA-DB web server towards 18 known anti-diabetes protein targets. More than 20% of all compounds could bind to more than five diabetes targets with high binding affinity (<−9.0 kcal/mol). Filtering with physicochemical and pharmacokinetic properties, including ADMET parameters, 12 compounds were identified as potential anti-T2DM with favorable ADMET properties. Six of those compounds, (2R)-7,4′-dihydroxy-5-methoxy-8-methylflavone; (RR)-(+)-3′-senecioylkhellactone; 2′,4′,6′-trihydroxy chalcone; alpinetin; pinobanksin-3-O-butyrate; and pinocembrin-5-methyl ether were first reported as anti-T2DM agents. We identified the significant T2DM targets of Asian propolis, namely retinol-binding protein-4 (RBP4) and aldose reductase (AKR1B1) that have important roles in insulin sensitivity and diabetes complication, respectively. Molecular dynamic simulations showed stable interaction of selected propolis compounds in the active site of RBP4 and AKR1B1. These findings suggest that Asian propolis compound may be effective for treatment of T2DM by targeting RBP4 and AKR1B1.

Mangifera indica as propolis source: what exactly do bees collect?

Objective

The mango tree Mangifera indica is known as one of the botanical sources of propolis in Tropical regions. There are two different materials which bees can collect from a mango tree to produce propolis: the resin of the tree bark, and the latex found on the fruits. We performed the study of the chemical profile of mango resin in comparison with propolis in order to clarify its importance as propolis source.

Results

We compared the chemical profiles (by GC–MS analysis of ethanol extracts after silylation) of the resin and samples of propolis: of stingless bees (3 Vietnames, 2 Indonesian), and one of Apis mellifera from Thailand. In the resin and all propolis samples, 25 compounds were identified: fatty acids, cardanols (alk(en)yl phenols), cardols, anacardic acids, triterpene alcohols and ketones, cycloartane type triterpenic acids. All samples have the same qualitative composition but there are important quantitative differences. Considering literature data on mango latex, we conclude that bees of different species, make use of the two propolis sources offered by mango: bark resin and fruit latex, in different proportions. We also confirmed for the first time the presence of alk(en)yl phenols and anacardic acids in the tree bark resin of mango.

Cytotoxicity effect of honey, bee pollen, and propolis from seven stingless bees in some cancer cell lines

Our effort to find new material for anti cancer from natural resources leads us to focus on stingless bee products such as honey, bee pollen, and propolis. The products were from seven stingless bees named Homotrigona fimbriata, Heterotrigona itama, Heterotrigona bakeri, Tetragonula sarawakensis, Tetragonula testaceitarsis, Tetragonula fuscobalteata, Tetragonula laeviceps. The stingless bee products were evaluated for their cytotoxicity effect on MCF-7, HeLa and Caco-2 cancer cell lines. This is the first time to be reported that the honey, ethanol extracts of bee pollen and propolis of H. fimbriata displayed more potent cytotoxicity than other stingless bee products. By chromatography and biological activity-guided fractionation, ethanol extract of propolis from H. fimbriata was fractionated and isolated its active compound named mangiferonic acid. Mangiferonic acid showed a cytotoxicity effect with IC₅₀ values 96.76 µM in MCF-7, >110.04 µM in HeLa, and > 110.04 µM in Caco-2, respectively. These results exhibited the potential of ethanol extracts from propolis of H. fimbriata to be further developed for drug and experiments to verify the function are essential.

Use of Stingless Bee Propolis and Geopropolis against Cancer-A Literature Review of Preclinical Studies

Cancer is one of the major maladies affecting humankind and remains one of the leading causes of death worldwide. The investigation of the biological activities of stingless bee products, especially propolis and geopropolis, has revealed promising therapeutic properties, especially in the research on new antineoplastic agents. This literature review of preclinical trials, involving biological assays of antitumor activity and identification of the chemical composition of propolis and geopropolis of stingless bee species, describes the cytotoxicity in tumor lineages (breast, lung, ovarian, liver, mouth, pharynx, larynx, colon, stomach, colorectal, cervix, kidney, prostate, melanoma, human glioblastoma, canine osteosarcoma, erythroleukemia, human chronic myelocytic leukemia, and human promyelocytic leukemia) of propolis and geopropolis of 33 species of stingless bees. The chemical composition of propolis and geopropolis was identified, indicating that these belong to the chemical classes of phenolic acids, flavonoids, coumarins, benzophenones, anthraquinones, alkaloids, terpenes, steroids, saponins, fatty acids, and carbohydrates and are possibly responsible for the cytotoxicity in tumor cells. Apoptosis was one of the main mechanisms of cytotoxicity of extracts and substances isolated from stingless bee products. Although the results found are encouraging, other preclinical studies and clinical trials are essential for the discovery of new anticancer agents.

Stingless Bee Propolis: New Insights for Anticancer Drugs

Natural products are important sources of biomolecules possessing antitumor activity and can be used as anticancer drug prototypes. The rich biodiversity of tropical and subtropical regions of the world provides considerable bioprospecting potential, including the potential of propolis produced by stingless bee species. Investigations of the potential of these products are extremely important, not only for providing a scientific basis for their use as adjuvants for existing drug therapies but also as a source of new and potent anticancer drugs. In this context, this article organizes the main studies describing the anticancer potential of propolis from different species of stingless bees with an emphasis on the chemical compounds, mechanisms of action, and cell death profiles. These mechanisms include apoptotic events; modulation of BAX, BAD, BCL2-L1 (BCL-2 like 1), and BCL-2; depolarization of the mitochondrial membrane; increased caspase-3 activity; poly (ADP-ribose) polymerase (PARP) cleavage; and cell death induction by necroptosis via receptor interacting protein kinase 1 (RIPK1) activation. Additionally, the correlation between compounds with antioxidant and anti-inflammatory potential is demonstrated that help in the prevention of cancer development. In summary, we highlight the important antitumor potential of propolis from stingless bees, but further preclinical and clinical trials are needed to explore the selectivity, efficacy, and safety of propolis.

Anticancer Activity of Propolis and Its Compounds

Propolis is a natural material that honey bees (Apis mellifera) produce from various botanical sources. The therapeutic activity of propolis, including antibacterial, antifungal, and anti-inflammatory effects, have been known since antiquity. Cancer is one of the major burdens of disease worldwide, therefore, numerous studies are being conducted to develop new chemotherapeutic agents and treatments for cancer. Propolis is a rich source of biologically active compounds, which affect numerous signaling pathways regulating crucial cellular processes. The results of the latest research show that propolis can inhibit proliferation, angiogenesis, and metastasis of cancer cells and stimulate apoptosis. Moreover, it may influence the tumor microenvironment and multidrug resistance of cancers. This review briefly summarizes the molecular mechanisms of anticancer activity of propolis and its compounds and highlights the potential benefits of propolis to reduce the side effects of chemotherapy and radiotherapy.

Propolis of stingless bees: A phytochemist's guide through the jungle of tropical biodiversity

BACKGROUND

Stingless bees (Meliponini), like honeybees Apis mellifera, collect plant resins in order to produce propolis (cerumen, geopropolis). This type of propolis has long been used in traditional medicine in Mexico, Brazil, Argentina, India, and Vietnam, as a remedy for improving health and treating various diseases. The scientific and commercial interest in stingless bee propolis has been steadily increasing over the last few years. The new and growing knowledge in this field requires systematising, as a basis for further work. Recent reviews of Meliponini propolis deal only with the South American and Mesoamerican species, while reviews of the Asian, Australian and African species are missing. Furthermore, the chemical composition has not been thoroughly reviewed since 2007.

PURPOSE

This review summarises and discusses the available data about the chemical composition of propolis from the stingless bee species (Meliponinae) of the Americas, Asia and Australia, published after 2007. The published information on the biological action of chemically characterised Meliponini propolis, and of individual constituents, is addressed. The plant sources of this propolis are also considered.

CONCLUSION AND PERSPECTIVES

Chemical studies of Meliponini propolis has resulted in the discovery of new natural molecules, some of them with valuable bioactivity. Moreover, finding known molecules in propolis stimulates the study of their pharmacological properties. The enormous chemical variability of stingless bee propolis is a challenge to chemists, entomologists and pharmacologists. It is essential to perform pharmacological studies with only chemically characterised propolis of stingless bees. Further studies are required to chemically characterise and scientifically support the medicinal properties of stingless bee propolis and to clarify the potential for its commercial use. This could lead to increased prices for Meliponinae propolis and provide an additional source of income for farmers in rural communities with most serious social needs.

Broad-spectrum pharmacological activity of Australian propolis and metabolomic-driven identification of marker metabolites of propolis samples from three continents

Propolis is a by-product of honeybee farming known for its broad therapeutic benefits around the world and is extensively used in the health food and beverage industry. Despite Australia being one of the world's megadiverse countries with rich flora and fauna, Australian propolis samples have not been explored adequately with most in vitro and in vivo studies centred on their Brazilian and Chinese counterparts. In view of this, our study was designed to investigate the chemical composition and anti-proliferative, antibacterial, antifungal, anti-inflammatory and antioxidant properties of Australian propolis (AP-1) extract to draw a comparison with Brazilian (BP-1) and Chinese propolis (CP-1) extracts. The AP-1 extract displayed significantly greater anti-proliferative activity against the MCF7 and the MDA-MB-231 metastatic breast adenocarcinoma cell lines compared to BP-1 and CP-1 (p < 0.05). Similar trends were also observed in the antibacterial (Escherichia coli and Staphylococcus aureus), anti-inflammatory (lipopolysaccharide-induced RAW264.7 macrophages) and antioxidant assays (ABTS, DPPH and CUPRAC) with AP-1 exhibiting more potent activity than BP-1 and CP-1. The ultra-high performance liquid chromatography (UPLC) coupled with quadrupole high-resolution time of flight mass spectrometry (qTOF-MS) and chemometrics implementing unsupervised PCA and supervised OPLS-DA analyses of the propolis samples from Australia, China and Brazil revealed 67 key discriminatory metabolites belonging to seven main chemical classes including flavonoids, triterpenes, acid derivatives, stilbenes, steroid derivatives, diterpenes and miscellaneous compounds. Additionally, seven common phenolic compounds were quantified in the samples. Further mechanistic studies are necessary to elucidate the modes of action of Australian propolis for its prospective use in the food, nutraceutical and pharmaceutical industries.

Panduratins Q-Y, dimeric metabolites from Boesenbergia rotunda and their antiausterity activities against the PANC-1 human pancreatic cancer cell line

A methanolic extract of the rhizomes of Boesenbergia rotunda showed potent preferential cytotoxicity against PANC-1 human pancreatic cancer cells under nutrient deficiency conditions with a PC₅₀ value of 6.6 μg/mL. Bioactivity-guided phytochemical investigation of the rhizomes of B. rotunda led to the isolation of nine undescribed dimeric metabolites, panduratins Q-Y. Their structures were elucidated based on NMR, MS, and ECD spectroscopic data interpretation. Panduratins Q-S and U-W exhibited potent cytotoxicity towards PANC-1 cell line with the PC₅₀ values ranging from 0.8 to 6.3 μM. Panduratin W, which possessed a cyclohexenylchalcone-linked flavanone skeleton, showed the most cytotoxicity with a PC₅₀ value of 0.8 μM under nutrient-deprived medium.

New dihydrochromene and xanthone derivatives from Lisotrigona furva propolis

A new dihydrochromene derivative, named lisofurvin (1) and a xanthone, named dihydrobrasixanthone B (2) together with twenty one known compounds (3-23) were isolated from propolis of the stingless bee Lisotrigona furva. Their chemical structures were determined by means of spectroscopic methods including 1D and 2D NMR, and MS. The chemical constituents are predominantly geranyl(oxy) xanthones and Cratoxylum cochinchinense was suggested as a resin source, besides two other plants Mangifera indica and dammar trees (Dipterocarpaceae). Compound 1 showed significant cytotoxic activity against KB, HepG-2, and Lu-1 cancer cell lines with IC₅₀ values range from 12.63 to 15.17 μg/mL. Several isolated compounds were active against one to four tested cancer cell lines. In addition, among the isolated compounds, α-mangostin (15) displayed the strongest antimicrobial activity against three Gram (+) strains, P. aeruginosa, and C. albicans with MIC values ranging between 1 and 2 μg/mL. Compound 22 showed good activity against three Gram (+) strains and C. albicans.

Ancistrobrevidines A-C and related naphthylisoquinoline alkaloids with cytotoxic activities against HeLa and pancreatic cancer cells, from the liana Ancistrocladus abbreviatus

From the leaves of Ancistrocladus abbreviatus (Ancistrocladaceae), six 5,1'-coupled naphthyldihydroisoquinoline alkaloids were isolated, ancistrobrevidines A-C (5-7), 5-epi-dioncophyllidine C₂ (10), 6-O-methylhamatinine (8), and 6-O-methylancistectorine A₃ (9); the two latter compounds were already known from related plants. Most strikingly, this series comprises alkaloids belonging to three different subclasses of naphthylisoquinolines. Ancistrobrevidine C (7) and the alkaloids 8 and 9, displaying the S-configuration at C-3 and an oxygen function at C-6, are three further representatives of the large subgroup of 5,1'-coupled Ancistrocladaceae-type compounds found in nature. 5-epi-Dioncophyllidine C₂ (10), lacking an oxygen function at C-6 and having the R-configuration at C-3, is only the third representative of a 5,1'-linked Dioncophyllaceae-type naphthylisoquinoline. Likewise rare are 5,1'-coupled hybrid-type alkaloids, which are 6-oxygenated and 3R-configured. The ancistrobrevidines A (5) and B (6) are the only second and third examples of such 5,1'-linked naphthylisoquinolines in Ancistrocladus species showing the landmarks of both, Ancistrocladaceae- and Dioncophyllaceae-type naphthylisoquinolines. In the roots of A. abbreviatus, two further unprecedented 5,1'-coupled alkaloids were discovered, ancistrobreviquinones A (11) and B (12), consisting of a 3,4-naphthoquinone portion coupled to a tetrahydroisoquinoline subunit. They are the very first quinoid naphthylisoquinolines possessing an ortho-diketone entity. Ancistrobrevidine C (7) exerted pronounced antiproliferative activities against HeLa cervical cancer cells and preferential cytotoxicity towards PANC-1 human pancreatic cancer cells under nutrient-deprived conditions following the antiausterity approach. Moreover, 7 suppressed the migration of PANC-1 cells and significantly inhibited colony formation under nutrient-rich conditions in a concentration-dependent manner, and induced dramatic alteration in cell morphology, leading to cell death.

Highly Potent Antiausterity Agents from Callistemon citrinus and Their Mechanism of Action against the PANC-1 Human Pancreatic Cancer Cell Line

Human pancreatic cancer cells display remarkable tolerance to nutrition starvation that help them to survive in a hypovascular tumor microenvironment, a phenomenon known as "austerity". The elucidation of agents countering this tolerance is an established antiausterity strategy in anticancer drug discovery. In this study, a Callistemon citrinus leaf extract inhibited the viability of PANC-1 human pancreatic cancer cells preferentially under nutrient-deprived medium (NDM) with a PC₅₀ value of 7.4 μg/mL. Workup of this extract resulted in the isolation of three new meroterpenoids, callistrilones L-N (1-3), together with 14 known compounds (4-17). The structure elucidation of the new compounds was achieved by HRFABMS and by NMR and ECD spectroscopic analysis. The new compounds showed highly potent preferential cytotoxicity against PANC-1 cells with PC₅₀ values ranging from 10 to 65 nM in NDM. Of these, callistrilone L (1) inhibited PANC-1 cell migration and colony formation in a normal nutrient-rich condition. Callistrilone L (1) also strongly suppressed the migration of PANC-1 cells in real time. Mechanistically, 1 was found to inhibit the Akt/mTOR and autophagy activation pathway. Callistrilone L (1) and related meroterpenoids are promising leads for anticancer drug development based on the antiausterity strategy used in this work.

Lessons from Exploring Chemical Space and Chemical Diversity of Propolis Components

Propolis is a natural resinous material produced by bees and has been used in folk medicines since ancient times. Due to it possessing a broad spectrum of biological activities, it has gained significant scientific and commercial interest over the last two decades. As a result of searching 122 publications reported up to the end of 2019, we assembled a unique compound database consisting of 578 components isolated from both honey bee propolis and stingless bee propolis, and analyzed the chemical space and chemical diversity of these compounds. The results demonstrated that both honey bee propolis and stingless bee propolis are valuable sources for pharmaceutical and nutraceutical development.

A new cytotoxic cardenolide from the roots of Calotropis gigantea

Bioactivity-guided isolation of the CHCl₃-soluble fraction of the roots of Calotropis gigantea was carried out to obtain a new cardenolide glycoside, caloside G. Its absolute structure was elucidated based on NMR and ECD spectroscopic data interpretation. Caloside G showed noteworthy cytotoxicity against the PANC-1 human pancreatic and HeLa human cervical carcinoma cell lines, with the submicromolar IC₅₀ values of 0.038 and 0.09 µM, respectively.

Antioxidant-Based Medicinal Properties of Stingless Bee Products: Recent Progress and Future Directions

Stingless bees are a type of honey producers that commonly live in tropical countries. Their use for honey is being abandoned due to its limited production. However, the recent improvements in stingless bee honey production, particularly in South East Asia, have brought stingless bee products back into the picture. Although there are many stingless bee species that produce a wide spread of products, known since old eras in traditional medicine, the modern medical community is still missing more investigational studies on stingless bee products. Whereas comprehensive studies in the current era attest to the biological and medicinal properties of honeybee (Apis mellifera) products, the properties of stingless bee products are less known. This review highlights for the first time the medicinal benefits of stingless bee products (honey, propolis, pollen and cerumen), recent investigations and promising future directions. This review emphasizes the potential antioxidant properties of these products that in turn play a vital role in preventing and treating diseases associated with oxidative stress, microbial infections and inflammatory disorders. Summarizing all these data and insights in one manuscript may increase the commercial value of stingless bee products as a food ingredient. This review will also highlight the utility of stingless bee products in the context of medicinal and therapeutic properties, some of which are yet to be discovered.

Antiausterity Activity of Secondary Metabolites from the Roots of Ferula hezarlalehzarica against the PANC-1 Human Pancreatic Cancer Cell Line

Human pancreatic cancer is one of the most aggressive types of cancer, with a high mortality rate. Due to the high tolerance of such cancer cells to nutrient starvation conditions, they can survive in a hypovascular tumor microenvironment. In this study, the dichloromethane extract of the roots of Ferula hezarlalehzarica showed potent preferential cytotoxic activity with a PC₅₀ value of 0.78 μg/mL. Phytochemical investigation of this extract led to the isolation of 18 compounds, including one new sesquiterpenoid (6) and one new monoterpenoid (18). All isolated compounds were evaluated for their preferential cytotoxicity against PANC-1 human pancreatic cancer cells by employing an antiausterity strategy. Among them, ferutinin (2) was identified as the most active compound, with a PC₅₀ value of 0.72 μM. In addition, the real-time effect of ferutinin (2) and compound 6 against PANC-1 cells, exposed to a nutrient-deprived medium (NDM), showed cell shrinkage, leading to cancer cell death within a short period of exposure. Compounds 2 and 6 also inhibited colony formation of PANC-1 cells. The present study indicates that the dichloromethane extract of the roots of F. hezarlalehzarica is a rich source of bioactive compounds for targeting PANC-1 cells.

Phytochemical and biological studies on rare and endangered plants endemic to China. Part XIV. Structurally diverse terpenoids from the twigs and needles of the endangered plant Picea brachytyla

A phytochemical investigation on the MeOH extract of the twigs and needles of the endangered plant Picea brachytyla led to the isolation and characterization of thirty-eight structurally diverse terpenoids. Seven of these molecules are previously undescribed, including three abietane-type (brachytylins A-C) and one labdane-type (brachytylin D) diterpenoids, an unseparated C-24 epimeric mixture of cycloartane-type triterpenoids (brachytylins E/F, ratio: 1:1), and a rare rearranged 12(1 → 6)-abeo-megastigmane glycoside (brachytylins G). Their structures and absolute configurations were determined by extensive spectroscopic (e.g., detailed 2D NMR and ECD) methods and/or X-ray diffraction analyses. All the isolates were evaluated for their inhibitory activities against the adenosine triphosphate (ATP)-citrate lyase (ACL) and the Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2). Among them, abiesadine J showed inhibitory effect against ACL, displaying an IC₅₀ value of 17 μM. 3S,23R-Dihydroxycycloart-24-en-26-oic acid exhibited inhibitory effect on SHP2, with an IC₅₀ value of 19 μM. Meanwhile, 3R*,23S*-dihydroxycycloart-24-en-26-oic acid was found to have inhibitory effects against both ACL and SHP2, with IC₅₀ values of 16 and 12 μM, respectively.

Post-genomic approach based discovery of alkylresorcinols from a cricket-associated fungus, Penicillium soppi

Polyketide synthase (PKS) gene-guided genome mining in a cricket-associated fungus, Penicillium soppi, revealed a cryptic biosynthetic gene cluster that contained a highly reducing PKS (HR-PKS), a type III PKS, and a P450 gene. Heterologous expression of the cluster in Aspergillus oryzae led to the isolation of novel alkylresorcinols with a unique Z,E,Z-triene motif. This study displays an unusual biosynthetic mechanism of an HR-PKS and a new releasing mechanism via a type III PKS in fungi.

Ealamines A-H, a Series of Naphthylisoquinolines with the Rare 7,8'-Coupling Site, from the Congolese Liana Ancistrocladus ealaensis, Targeting Pancreatic Cancer Cells

From the twigs and leaves of the Central African liana Ancistrocladus ealaensis (Ancistrocladaceae), a series of ten 7,8'-coupled naphthylisoquinoline alkaloids were isolated, comprising eight new compounds, named ealamines A-H (4a, 4b, 5-10), and two known ones, 6-O-demethylancistrobrevine A (11) and yaoundamine A (12), which had previously been found in related African Ancistrocladus species. Only one of the new compounds within this series, ealamine H (10), is a typical Ancistrocladaceae-type alkaloid, with 3S-configuration at C-3 and an oxygen function at C-6, whereas seven of the new alkaloids are the first 7,8'-linked "hybrid-type" naphthylisoquinoline alkaloids, i.e., 3R-configured and 6-oxygenated in the tetrahydroisoquinoline part. The discovery of such a broad series of 7,8'-coupled naphthyltetrahydroisoquinolines is unprecedented, because representatives of this subclass of alkaloids are normally found in Nature quite rarely. The stereostructures of the new ealamines were assigned by HRESIMS, 1D and 2D NMR, oxidative degradation, and experimental and quantum-chemical ECD investigations, and-in the case of ealamine A (4a)-also confirmed by X-ray diffraction analysis. Ealamines A-D exhibited distinct-and specific-antiplasmodial activities, and they displayed pronounced preferential cytotoxic effects toward PANC-1 human pancreatic cancer cells in nutrient-deprived medium, without causing toxicity under normal, nutrient-rich conditions, with ealamine C (5) as the most potent agent.

Phytochemical analysis of Vietnamese propolis produced by the stingless bee Lisotrigona cacciae

Propolis produced by the stingless bee Lisotrigona cacciae was studied for the first time. Using different chromatographic procedures, a total of eighteen constituents (phenols and triterpenes) were isolated, among which flavane 1, homoisoflavanes 2-4, and xanthones 5 and 6 were new for propolis. Propolis extract was also characterized by gas chromatography/mass spectrometry and other fifteen constituents were identified. The xanthone α-mangostin (8) demonstrated significant activity against Staphylococcus aureus with MIC and MBC 0.31 μg/ml, followed by 7,4'-dihydroxy-5-methoxy-8-methylflavane (1) with MIC 78 μg/ml and MBC 156 μg/ml. 10,11- Dihydroxydracaenone C (4), a component bearing ortho-hydroxyl groups, was the only compound displaying radical scavenging ability. Triple botanical origin of the sample was defined, consisting of Dracaena cochinchinensis, Cratoxylum cochinchinense and Mangifera indica. D. cochinchinensis is a new resin source of propolis.

Cycloartane-Type Triterpenes and Botanical Origin of Propolis of Stingless Indonesian Bee Tetragonula sapiens

This study clarifies the chemical constituents and botanical origin of Tetragonula sapiens Cockerell bee propolis collected from Southeast Sulawesi, Indonesia. Propolis samples and resin of Mangifera indica were extracted with 99% ethanol to obtain an ethanol extract of propolis (EEP) and an ethanol extract of M. indica resin (EEM). Column chromatography, thin-layer chromatography (TLC), and high-performance liquid chromatography (HPLC) were developed and used for the separation and isolation of compounds from the ether-soluble fraction. The structure of the compounds was determined by nuclear magnetic resonance (NMR) spectroscopic analysis, and their molecular weight analyzed by gas chromatography–mass spectrometry (GC–MS). The HPLC chromatogram of the EEP was then compared with the HPLC chromatogram of EEM to investigate the botanical origin of propolis. Five compounds were isolated from the EEP, and their structures were determined as mangiferolic acid, cycloartenol, ambonic acid, mangiferonic acid, and ambolic acid, which are cycloartane-type triterpenes. The characteristic peak of the HPLC chromatograms of EEP and EEM showed a similar pattern, which is that the main components of propolis were also found in M. indica resin. These results suggested that the propolis from Southeast Sulawesi was rich in cycloartane-type triterpenes, and the plant source of the propolis could be Mangifera indica (mango).

Ancistrolikokine E3, a 5,8'-Coupled Naphthylisoquinoline Alkaloid, Eliminates the Tolerance of Cancer Cells to Nutrition Starvation by Inhibition of the Akt/mTOR/Autophagy Signaling Pathway

PANC-1 human pancreatic cancer cells are characterized by their ability to proliferate aggressively under hypovascular and hypoxic conditions in the tumor microenvironment, displaying a remarkable tolerance to nutrition starvation. The antiausterity strategy is a new approach in anticancer drug discovery aiming at the identification of potent agents that inhibit preferentially the survival of tumor cells during a limited supply of nutrients and oxygen. The new 5,8'-coupled naphthyldihydroisoquinoline alkaloid ancistrolikokine E₃ (4), isolated from the Congolese liana Ancistrocladus likoko, showed potent preferential cytotoxicity against PANC-1 cells under nutrient-deprived conditions, with a PC₅₀ value of 2.5 μM, without exhibiting toxicity in normal, nutrient-rich medium. The compound was found to induce dramatic alterations in cell morphology, leading to cell death. Moreover, it inhibited significantly PANC-1 cell migration and colony formation in a concentration-dependent manner. This study on 4 provides the first live evidence of the effect of a naphthyldihydroisoquinoline alkaloid against PANC-1 cells in nutrient-deprived medium. Mechanistic investigations conducted suggest that compound 4 is a potent inhibitor of the activation of the Akt/mTOR pathway. Furthermore, it inhibited the expression levels of the key autophagy regulators Atg5, Atg12, Beclin-1, LC3-I, and LC3-II. The results demonstrated that ancistrolikokine E₃ (4) is a potent early-stage inhibitor of the autophagy pathway in PANC-1 human pancreatic cancer cells. Ancistrolikokine E₃ (4) and related naphthylisoquinoline alkaloids are promising potential lead compounds for anticancer drug development based on the antiausterity strategy.

A New Alkenylphenol from the Propolis of Stingless Bee Trigona minor

A new alkenylphenol, 2-hydroxyl-6-(14' Z -nonadecenyl)benzoic acid (1), was isolated from the ethanolic extract of Vietnamese stingless bee propolis Trigona minor (Meliponini, Apidae), together with two known compounds (2 and 3). Their chemical structures were determined by extensive NMR spectroscopic analysis. All compounds were tested for preferential cytotoxicity against the PANC-1 human pancreatic cell line under nutrition-deprived conditions (NDM). Compound 1 exhibited the strongest preferential cytotoxicity, with a PC50 value of 2.4 μM.