Antileishmanial polyphenols from Corymbia maculata

Exploring the Anti-Inflammatory Potential of Australian Native Plants Based on their Ethnopharmacological Knowledge

Inflammation represents the inherent protective reaction of the human body to various harmful agents and noxious stimuli. Standard anti-inflammatory therapy including nonsteroidal anti-inflammatory drugs are associated with several side effects. In the past decades, people rely on medicinal plants for the treatment of inflammation. The traditional utilization of medicinal plants is regarded as a safe, cost-effective, and broadly accepted approach. In this study, anti-inflammatory activity of plants traditionally utilized by the D'harawal people in Australia has been assessed in vitro. Eighty Australian native plants were screened based on the Dharawal Pharmacopeia for their inhibitory effect on the nitric oxide (NO) production in lipopolysaccharides (LPS) and interferon (IFN)-γ stimulated RAW 264.7 murine macrophages for their anti-inflammatory activity. From the eighty ethanolic extracts screened, seventeen displayed potent NO inhibition with an IC50 recorded below 15 μg/mL. The aim of this review was to utilise the ethnopharmacological knowledge and to correlate the anti-inflammatory activity of the seventeen plants with either their known or unknown phytochemicals reported in the literature. In doing so, we have created a snapshot of Australian native plant candidates that warrant further chemical investigation associated with their anti-inflammatory activity.

Synergistic antileishmanial activity of erythrodiol, uvaol, and oleanolic acid isolated from olive leaves of cv. Chemlali

This study aimed to assess the antileishmanial activity of biomolecules obtained from Olea europaea L. leaves and twigs recovered from eight Tunisian cultivars. The extraction was first carried out with 80% methanol, and then the obtained extract was fractionated using three solvents of increasing polarity: cyclohexane (CHX), dichloromethane (DCM) and ethyl acetate (EtOAc). The antileishmanial activity was determined against leishmanial strains responsible for cutaneous, visceral, and mucocutaneous leishmaniasis. The cyclohexane fraction of the leaves of cv. Chemlali from the region of Sidi-Bouzid exhibited the strongest leishmanicidal activity against all the tested leishmanial strains. The inhibition concentrations (IC50) were 16.5, 14.5, and 7.4 μg mL-1 for Leishmania mexicana (cutaneous), Leishmania braziliensis (mucocutaneous), and Leishmania donovani (visceral), respectively. Interestingly, low cytotoxicity was observed on THP-1 cells with selective indexes (SI) ranging from 22.8 to 50.5. HPLC-HRMS and full-house NMR analysis allowed the identification of three triterpenic compounds, oleanolic acid (IC50 = 64.1 μg mL-1), erythrodiol (IC50 = 52.0 µg mL-1), and uvaol (IC50 = 53.8 μg mL-1). Antileishmanial activity of uvaol and oleanolic acid has been previously reported. However, this work constitutes the first report of the antileishmanial activity of erythrodiol which showed combinatorial interaction with uvaol (IC50 = 26.1 μg mL-1) against Leishmania tropica. The mixture of the three compounds, as major ones, exhibited an enhanced activity against Leishmania tropica (IC50 = 16.3 µg mL-1) compared to erythrodiol alone or the combination of uvaol and erythrodiol. This finding is of great importance and needs further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03825-3.

The Ethnopharmacology, Phytochemistry and Bioactivities of the Corymbia Genus (Myrtaceae)

Plants have been vital to human survival for aeons, especially for their unique medicinal properties. Trees of the Eucalyptus genus are well known for their medicinal properties; however, little is known of the ethnopharmacology and bioactivities of their close relatives in the Corymbia genus. Given the current lack of widespread knowledge of the Corymbia genus, this review aims to provide the first summary of the ethnopharmacology, phytochemistry and bioactivities of this genus. The Scopus, Web of Science, PubMed and Google Scholar databases were searched to identify research articles on the biological activities, phytochemistry and ethnomedical uses of Corymbia species. Of the 115 Corymbia species known, 14 species were found to have ethnomedical uses for the leaves, kino and/or bark. Analysis of the references obtained for these 14 Corymbia spp. revealed that the essential oils, crude extracts and compounds isolated from these species possess an array of biological activities including anti-bacterial, anti-fungal, anti-protozoal, anti-viral, larvicidal, insecticidal, acaricidal, anti-inflammatory, anti-oxidant, anti-cancer and anti-diabetic activities, highlighting the potential for this under-studied genus to provide lead compounds and treatments for a host of medical conditions.

Synthesis and Cytotoxic Activities of 8- and 6-Demethyleucalyptins

Secondary metabolites in plants influence the health of herbivores such as Japanese rock ptarmigans that feed on the leaves and fruits of alpine plants. Thus, it is important to understand the secondary metabolites of alpine plants and their biological activities for conserving Japanese rock ptarmigans. We isolated C-methylflavone from the leaves of Kalmia procumbens, on which Japanese rock ptarmigans feed. Although its structure was deduced to be 8-demethyleucalyptin by comparing its NMR data with the reported ones, the possibility that the isolated compound is 6-demethyleucalyptin cannot be ruled out. Thus, both isomers were synthesized. The isolated compound was unambiguously determined to be 8-demethyleucalyptin by comparing its NMR data with those of the synthetic ones. Cytotoxic evaluation of 8- and 6-demethyleucalyptins revealed that only the former showed cytotoxicity against HCT116 and MRC-5 cells. The present study provides not only easy access to 8- and 6-demethyleucalyptins, but also their biological information.

Antioxidant and Anticholinesterase Activities of Extracts and Phytochemicals of Syzygium antisepticum Leaves

Bioassay-guided separation of young leaves extracts of Syzygium antisepticum (Blume) Merr. & L.M. Perry led to the isolation of four triterpenoids (betulinic acid, ursolic acid, jacoumaric acid, corosolic acid) and one sterol glucoside (daucosterol) from the ethyl acetate extract, and three polyphenols (gallic acid, myricitrin, and quercitrin) from the methanol (MeOH) extract. The MeOH extract of S. antisepticum and some isolated compounds, ursolic acid and gallic acid potentially exhibited acetylcholinesterase activity evaluated by Ellman’s method. The MeOH extract and its isolated compounds, gallic acid, myricitrin, and quercitrin, also strongly elicited DPPH radical scavenging activity. In HEK-293 cells, the MeOH extract possessed cellular antioxidant effects by attenuating hydrogen peroxide (H₂O₂)-induced ROS production and increasing catalase, glutathione peroxidase-1 (GPx-1), and glutathione reductase (GRe). Furthermore, myricitrin and quercitrin also suppressed ROS production induced by H₂O₂ and induced GPx-1 and catalase production in HEK-293 cells. These results indicated that the young leaves of S. antisepticum are the potential sources of antioxidant and anticholinesterase agents. Consequently, S. antisepticum leaves are one of indigenous vegetables which advantage to promote the health and prevent diseases related to oxidative stress.

LC-ESI-QTOF-MS for the Profiling of the Metabolites and in Vitro Enzymes Inhibition Activity of Bryophyllum pinnatum and Oxalis corniculata Collected from Ramechhap District of Nepal

The objective of this study was to profile the chemical components and biological activity analysis of crude extract of Bryophyllum pinnatum and Oxalis corniculata. Results revealed that the analyzed plant materials encompass the high amount of total phenolic and flavonoids content and have significant antioxidant activities. Furthermore, methanol extracts are the potential source of α-amylase, α-glucosidase, lipase, tyrosinase and elastase inhibitors. High resolution mass spectrometry revealed the presence of diverse metabolites such as quercetin 3-O-α-L-rhamnopyranoside, myricetin 3-rhamnoside, bersaldegenin 1,3,5-orthoacetate, bryophyllin C, syringic acid, caffeic acid, p-coumaric acid, and quercetin in B. pinnatum and isoorientin, swertisin, apigenin 7,4'-diglucoside, vitexin, 4-hydroxybenzoic acid, vanillic acid, ethyl gallate, 3,3',4'-trihydroxy-5,7-dimethoxyflavone, and diosmetin-7-O-β-D-glucopyranoside in O. corniculata. Our finding suggested that these two plant species have high medicinal importance and are potential source of inhibitors for modern pharmaceuticals, nutraceuticals and cosmetics industries.

Prenylated Acetophloroglucinol Dimers from Acronychia trifoliolata: Structure Elucidation and Total Synthesis

The isolation of 12 secondary metabolites, including seven new acetophenone monomers, from the 50% CH3OH/CH2Cl2 extract (N089419-L/6) of Acronychia trifoliolata was reported previously. In the present work, three new prenylated acetophenone dimers (1-3) and five known dimers (4-8) were isolated, and their structures were elucidated by using various NMR spectroscopic techniques and HRMS. Among the new dimers, an unprecedented 4-isobutyl-3-isopropyltetrahydro-2H-pyran ring was observed in the structure of 1. This study is the first to report the formation of a 2H-pyran ring between two prenylated acetophloroglucinols. Only four related dimers have been reported before, and they were formylated phloroglucinol dimers from the family Eucalypteae. Compounds 2 and 3 are acrovestone-like dimers, and the structure of 3 was confirmed by total synthesis. The evaluation of the antiproliferative activity of isolated and synthesized acrovestone-like dimers indicated that a double bond in the prenyl-like moiety as found in the more active compounds might be important for mediating activity, while the pendant isobutyl group seems to be less important.

Flavonoids, antioxidant potential and antimicrobial activity of Myrcia rufipila mcvaugh leaves (myrtaceae)

This paper reports the first chemical study of the non-volatile compounds, antioxidant capacity and antimicrobial effect of the methanol extract of the leaves of Myrcia rufipila McVaugh. Samples of the leaves were collected in Maracanã Municipality, Pará, Brazil. The chemical investigation led to the identification of the triterpenoids β- and α-amyrin, the flavonoids 4'-O-galloyldihydromyricetin, myricetin, myricitrin, desmantin-I, myricetin-3-O-(3"-O-galloyl)-α-L-rhamnopyranoside and isovitexin, in addition to gallic acid. The methanol extract showed antioxidant capacity (>90%) against DPPH radical (IC₅₀ 356.3 ± 3.1 μg.mL^-1) and was active only at high concentrations against the tested microorganisms, including the chloramphenicol resistant E. coli CCMB261 and S. aureus CCMB285 and a nystatin resistant C. parapsilosis CCMB 288. This study shows that M. rufipila, like other Myrcia species, is another source of flavonoids such as desmantin-I and myricitrin which have shown hypoglycemic potential, besides triterpenes and phenolic acids.

Flavonoids as efficient scaffolds: Recent trends for malaria, leishmaniasis, Chagas disease, and dengue

Endemic in 149 tropical and subtropical countries, neglected tropical diseases (NTDs) affect more than 1 billion people annually with over 500,000 deaths. Among the NTDs, some of the most severe consist of leishmaniasis, Chagas disease, and dengue. The impact of the combined NTDs closely rivals that of malaria. According to the World Health Organization, 216 million cases of malaria were reported in 2016 with 445,000 deaths. Current treatment options are associated with various limitations including widespread drug resistance, severe adverse effects, lengthy treatment duration, unfavorable toxicity profiles, and complicated drug administration procedures. Flavonoids are a class of compounds that has been the subject of considerable scientific interest. New developments of flavonoids have made promising advances for the potential treatment of malaria, leishmaniasis, Chagas disease, and dengue, with less toxicity, high efficacy, and improved bioavailability. This review summarizes the current standings of the use of flavonoids to treat malaria and neglected diseases such as leishmaniasis, Chagas disease, and dengue. Natural and synthetic flavonoids are leading compounds that can be used for developing antiprotozoal and antiviral agents. However, detailed studies on toxicity, pharmacokinetics, and mechanisms of action of these compounds are required to confirm the in vitro pharmacological claims of flavonoids for pharmaceutical applications. HIGHLIGHTS: In the current review, we have tried to compile recent discoveries on natural and synthetic flavonoids as well as their implication in the treatment of malaria, leishmaniasis, Chagas disease, and dengue. A total of 373 (220 natural and 153 synthetic) flavonoids have been evaluated for antimalarial, antileishmanial, antichagasic, and antidengue activities. Most of these flavonoids showed promising results against the above diseases. Reports on molecular modeling of flavonoid compounds to the disease target indicated encouraging results. Flavonoids can be prospected as potential leads for drug development; however, more rigorously designed studies on toxicity and pharmacokinetics, as well as the quantitative structure-activity relationship studies of these compounds, need to be addressed.

HR-LC-ESI-Orbitrap-MS based metabolite profiling of Prunus dulcis Mill. (Italian cultivars Toritto and Avola) husks and evaluation of antioxidant activity

INTRODUCTION

Prunus dulcis Mill. is a plant cultivated for the production of its edible seeds, known as sweet almonds. In the last decades almond demand has highly increased due to their wide use in the industrial manufacturing of almond-based foods; this has led to a huge production of waste materials, mainly corresponding to shells and husks.

OBJECTIVE

To achieve a deeper understanding of the chemical composition of almond husks with the aim of exploring these byproducts as a source of bioactives to be used in nutraceutical and cosmetic formulations.

METHODS

Methanol, ethanol and ethanol-water extracts of the almond husks were analysed by high-resolution liquid chromatography electrospray ionisation Orbitrap mass spectrometry (HR-LC-ESI-Orbitrap-MS) in negative ion mode. Tandem mass spectrometry (MS/MS) data were acquired by using the Data-Dependent Scan experiment, allowing the precursor ion to be selected as the most intense peak during LC-MS analyses. Nuclear magnetic resonance (NMR) experiments were performed on a Bruker DRX-600 spectrometer. Folin-Ciocalteu, DPPH^• (2,2-diphenyl-1-picrylhydrazyl) and TEAC (Trolox equivalent antioxidant capacity) assays were employed to determine the total phenolic content and the radical scavenging activity of the extracts.

RESULTS

The LC-MS/MS analysis of the methanol extract guided the isolation of phloroglucinol derivatives, flavonoids and terpenes. Eco-friendly extraction methods showed to be selective in extracting flavonoids while the comparison of the LC-MS profiles of the Italian cultivars Toritto and Avola showed significant differences, confirming how different growing conditions may influence the metabolome of a plant species.

CONCLUSION

This study led to a deeper insight into the chemical constituents of almond husks and showed how the eco-friendly extraction resulted in an effective method to obtain extracts rich in antioxidant sources.

Antileishmanial, antioxidant, and cytotoxic activities of Quercus infectoria Olivier extract

Currently, there is no effective vaccine available, and chemotherapy is the main approach for treatment of cutaneous leishmaniasis (CL). During recent decades, studies have demonstrated that a number of plant-derived compounds may act as new therapeutic tools against leishmaniasis. This study was evaluated the antileishmanial, antioxidant, and cytotoxic activities of Quercus infectoria Olivier (oak) extract. The total amount of phenolic and flavonoid compounds was measured in oak extract. High performance liquid chromatography (HPLC) analysis was also performed to determine the amount of quercetin and gallic acid in this plant. This extract (0-80g/mL) was evaluated in vitro against promastigote and intracellular amastigote forms of Leishmania major (MRHO/IR/75/ER) using MTT assay and in a macro-phage model, respectively. Then oak extract was tested on CL in infected male BALB/c mice with L. major in order to evaluate the antileishmanial activity topically. Moreover, cytotoxicity effects of oak in murine macrophage cells were tested by MTT assay. Antioxidative activity of oak was also determined by the 2,2-diphenyl-1,1-picrylhydrazyl (DPPH) scavenging test. The amount of phenolic and flavonoid compounds in the oak extract was 57.50 and 1.86%, respectively. The amount of quercetin and gallic acid in the oak extract was 0.0064 and 0.22%, respectively. The findings revealed that oak significantly (P<0.05) inhibited the growth rate of promastigote of (IC50 12.65μg/mL) and amastigotes (IC50 10.31μg/mL) as a dose-dependent response. In the in vivo assay, after 4 weeks of treatment, 91.6, 66.66, and 50% recovery was observed in the infected mice treated with 20, 10, and 5mg/kg of oak extract, respectively. After treatment of the infected mice with the concentration of 10 and 20mg/kg of oak, the mean diameter of lesions, parasite load and mean number of parasites was significantly (P<0.05) reduced. Selectivity index of greater than 10 for oak revealed that oak extract had no cytotoxic effects on macrophage cells. Moreover, DPPH test demonstrated that radical inhibition occurred at greater power with increasing the concentration of oak. To conclude, the present study showed potent antileishmanial and antioxidant activity of oak extract; whereas this plant had no toxic effect on mammalian cells.

Phytochemical Profiling and Evaluation of Pharmacological Activities of Hypericum scabrum L

Phytochemical investigations of ethyl acetate-soluble part of the aerial part of Hypericum scabrum L. delivered eight pure phenolic compounds 1–8. The pure compounds were identified through physico-chemical, NMR (1D, 2D) and mass spectrometric studies as: 3-8′′-bisapigenin (1), quercetin (2), quercetin-3-O-α-l-arabinofuranoside (3), quercetin-3-O-α-l-rhamnoside (4), quercetin-3-O-β-d-glucopyranoside (5), quercetin-3-O-β-d-galactopyranoside (6), (−)-epicatechin (7), (+)-catechin (8). Total polyphenolic compounds and total flavonoids contents were determined in the extract as 0.107 mg∙mg⁻¹ and 0.023 mg∙mg⁻¹ of the dried extract, respectively. Antioxidant activity using DPPH free radical scavenging assay delivered very strong activity for compounds 2 and 5, 6 and crude extract 10. Protein tyrosine phosphatase 1B (PTP-1B) inhibition experiment of isolated compounds and crude extracts resulted in significant inhibition activity for samples 2, 7a, 8a, 11 and 12 with IC₅₀ values ranging from 1.57 to 2.91 µM. Antimicrobial activity of the pure compounds and extracts produced average results against Staphylococcus aureus, Escherichia coli and Candida albicans strains. From our literature survey, it appears that all pure compounds except 2 were isolated and reported for the first time in H. scabrum.

Antileishmanial drug discovery: comprehensive review of the last 10 years

This review covers the current aspects of leishmaniasis including marketed drugs, new antileishmanial agents, and possible drug targets of antileishmanial agents.