Structurally diverse alkaloids from the Buxus sinica and their cytotoxicity

Extensive phytochemical study of the methanol extract of twigs and leaves of Buxus sinica resulted in the identification of forty-one Buxus alkaloids, including twenty undescribed ones, namely cyclobuxusinines A-I (1-7, 16 and 20), as well as secobuxusinines A-K (8-15 and 17-19). Their structures were delineated by detailed analysis using various spectroscopic techniques. cyclobuxusinines B (2) was the first Buxus alkaloid, whose CH3-18 was oxidized, implying the presence of special oxidative enzymes in this plant. Secobuxusinines C (10), D (11), and E (12), whose C-12 or C-19 have an OH group substitution, enriched the substituent pattern in Buxus alkaloid and suggested more structurally diverse alkaloids in the Buxus spp. In the assessment of their bioactivities, some of them exhibited significant cytotoxic effects on two human tumor ovarian cancer cell lines. Notably, compound 36 displayed more potent cytotoxic effect against ES2 and A2780 cell lines with the IC50 value of 1.33 μM and 0.48 μM, respectively.

Alkaloids as drug leads in Alzheimer's treatment: Mechanistic and therapeutic insights

Alzheimer's disease (AD) has few effective treatment options and continues to be a major global health concern. AD is a neurodegenerative disease that typically affects elderly people. Alkaloids have potential sources for novel drug discovery due to their diverse chemical structures and pharmacological activities. Alkaloids, natural products with heterocyclic nitrogen-containing structures, are considered potential treatments for AD. This review explores the neuroprotective properties of alkaloids in AD, focusing on their ability to regulate pathways such as amyloid-beta aggregation, oxidative stress, synaptic dysfunction, tau hyperphosphorylation, and neuroinflammation. The FDA has approved alkaloids such as acetylcholinesterase inhibitors like galantamine and rivastigmine. This article explores AD's origins, current market medications, and clinical applications of alkaloids in AD therapy. This review explores the development of alkaloid-based drugs for AD, focusing on pharmacokinetics, blood-brain barrier penetration, and potential adverse effects. Future research should focus on the clinical evaluation of promising alkaloids, developing recently discovered alkaloids, and the ongoing search for novel alkaloids for medical treatment. A pharmaceutical option containing an alkaloid may potentially slow down the progression of AD while enhancing its symptoms. This review highlights the potential of alkaloids as valuable drug leads in treating AD, providing a comprehensive understanding of their mechanisms of action and therapeutic implications.

Structurally modified Cyclovirobuxine-D Buxus alkaloids as effective analgesic agents through Cav3.2 T-Type calcium channel inhibition

Cyclovirobuxine-D (CVB-D) is a Buxus alkaloid and a major active constituent in the Chinese medicinal herb Buxus microphylls. Traditionally, the natural alkaloid cyclovirobuxine-D has a long history of use as a traditional Chinese medicine for cardiovascular diseases as well as to treat a wide variety of medical conditions. As we found that CVB-D inhibited T-type calcium channels, we designed and synthesized a variety of fragments and analogues and evaluated them for the first time as new Cav3.2 inhibitors. Compounds 2-7 exhibited potency against Cav 3.2 channels, and two of them were more active than their parent molecules. As a result of the in vivo experiments, both compounds 3 and 4 showed significantly reduced writhes in the acetic acid-induced writhing test. Studies of molecular modeling have identified possible mechanism(s) of Cav3.2 binding. Moreover, the relationship between structure and activity was studied in a preliminary manner. Our results indicated that compounds 3 and 4 could play an important role in the discovery and development of novel analgesics.

Chemistry and bioactivities of natural steroidal alkaloids

Steroidal alkaloids possess the basic steroidal skeleton with a nitrogen atom in rings or side chains incorporated as an integral part of the molecule. They have demonstrated a wide range of biological activities, and some of them have even been developed as therapeutic drugs, such as abiraterone acetate (Zytiga^®), a blockbuster drug, which has been used for the treatment of prostate cancer. Structurally diverse natural steroidal alkaloids present a wide spectrum of biological activities, which are attractive for natural product chemistry and medicinal chemistry communities. This review comprehensively covers the structural classification, isolation and various biological activities of 697 natural steroidal alkaloids discovered from 1926 to October 2021, with 363 references being cited.

Antiprotozoal Nor-Triterpene Alkaloids from Buxus sempervirens L

Malaria and human African trypanosomiasis (HAT; sleeping sickness) are life-threatening tropical diseases caused by protozoan parasites. Due to limited therapeutic options, there is a compelling need for new antiprotozoal agents. In a previous study, O-tigloylcyclovirobuxeine-B was recovered from a B. sempervirens L. (common box; Buxaceae) leaf extract by bioactivity-guided isolation. This nor-cycloartane alkaloid was identified as possessing strong and selective in vitro activity against the causative agent of malaria tropica, Plasmodium falciparum (Pf). The purpose of this study is the isolation of additional alkaloids from B. sempervirens L. to search for further related compounds with strong antiprotozoal activity. In conclusion, 25 alkaloids were obtained from B. sempervirens L., including eight new natural products and one compound first described for this plant. The structure elucidation was accomplished by UHPLC/+ESI-QqTOF-MS/MS and NMR spectroscopy. The isolated alkaloids were tested against Pf and Trypanosoma brucei rhodesiense (Tbr), the causative agent of East African sleeping sickness. To assess their selectivity, cytotoxicity against mammalian cells (L6 cell line) was tested as well. Several of the compounds displayed promising in vitro activity against the pathogens in a sub-micromolar range with concurrent high selectivity indices (SI). Consequently, various alkaloids from B. sempervirens L. have the potential to serve as a novel antiprotozoal lead structure.

Structurally diverse alkaloids from Buxus sempervirens with cardioprotective activity

Extensive phytochemical study of the methanol extract of twigs and leaves of Buxus sempervirens resulted in the identification of 17 Buxus alkaloids, including 12 new ones, namely buxusemines A-L (1-12). Their structures were delineated by detailed analysis of the HRESIMS and NMR data, as well as quantum chemical NMR calculations. Buxusemine A (1) represents the second Buxus alkaloid with a unique spiro[4.6]undecatriene moiety, buxusemines B-C (2-3) are a rarely occurring class of Buxus alkaloids featured with an additional five-membered ring through the ether or lactone linkage between C-10 and C-23, and buxusemines D-F (4-6) are another rare type of Buxus alkaloids with an epoxy motif. In the assessment of their bioactivities, buxusemine F (6) and buxanoldine (17) displayed more potent protective effects than the positive control cyclovirobuxinum D in the doxorubicin-induced cardiac injury model.

Buxaustroines A-N, a Series of 17(13→18)abeo-Cycloartenol Triterpenoidal Alkaloids from Buxus austro-yunnanensis and Their Cardioprotective Activities

Buxaustroines A-N (1-14), a series of triterpenoidal alkaloids featuring a novel 17(13→18)abeo motif, were obtained from the extract of Buxus austro-yunnanensis. Their structures were assigned based on NMR data analysis and X-ray diffraction crystallography. A putative biosynthetic pathway for one of the alkaloids from a co-isolate 15 is proposed. In the assessment of their bioactivities, some of the compounds displayed protective effects against doxorubicin-induced injury of myocardial cells. Preliminary structure-activity relationship studies of 1-14, which are based on the same skeleton, were conducted.

Two New Cytotoxic Steroidal Alkaloids from Sarcococca Hookeriana

Two new steroidal alkaloids, named hookerianine A (1) and hookerianine B (2) were isolated from the stems and roots of Sarcococca hookeriana Baill., along with two known compounds, sarcorucinine G (3) and epipachysamine D (4). On the basis of spectroscopic methods and by comparison with literature data, their structures were determined. As well as X-ray crystallography was performed to confirm compound 4. To identify novel antitumor inhibitors, all compounds were performed a CCK-8 assay against five human cancer cell lines SW480, SMMC-7721, PC3, MCF-7 and K562 in vitro. Compound 2 exhibited moderate cytotoxic activities to all cell lines with IC₅₀ values in the range of 5.97–19.44 μM. Compound 3 was the most effective one against SW480 and K562 cell lines with IC₅₀ values of 5.77 and 6.29 μM, respectively.

Skin Wound Healing Is Accelerated by a Lipid Mixture Representing Major Lipid Components of Chamaecyparis obtusa Plant Extract

In chronic nonhealing wounds, the healing process is disrupted and wounds are often infected with bacteria. About 85% of lower extremity amputations in diabetes are attributed to deep infection of foot ulcers. Therefore, infection control is critical for wound care. In this study, we analyzed lipid composition of Chamaecyparis obtusa extract, and we describe the wound-healing properties of its combination of 10 major lipid components. A 10-lipid mixture up-regulated HBD-3 and LL-37 through the olfactory receptor 2AT4 and induced phosphorylation of extracellular signal-regulated kinases and p38 mitogen-activated protein kinases in primary human keratinocytes. In addition, the 10-lipid mixture had direct bactericidal effects against Staphylococcus aureus and Streptococcus pyogenes and protected against staphylococcal α-toxin-induced keratinocyte cell death. In an animal model, the 10-lipid mixture accelerated skin wound healing and was also effective in healing wounds superinfected with S. aureus. We suggest that the 10-lipid mixture, because of its wound-healing and antimicrobial properties, can be beneficial for wound treatment.

A novel pregnane-type alkaloid from Pachysandra terminalis inhibits methicillin-resistant Staphylococcus aureus in vitro and in vivo

A new kind of pregnane-type alkaloid, 20α-dimethylamino-3β-senecioylamino-16β-hydroxy-pregn-5-ene (K-6), was isolated from Pachysandra terminalis Sieb. et Zucc., and its antibacterial activity against MRSA and MRSE was evaluated. We found that K-6 showed antibacterial effects against MRSA and MRSE with minimum inhibitory concentration values (25 mg/L), but did not induce antibiotic resistance in bacteria easily. The administration of K-6 dose-dependently improved the animal survival rate of mice infected with MRSA, with survival rates of 36.34% and 66.67% in the low-dose and high-dose groups, respectively. The protective effects were associated with the reduction of the bacterial titers in the blood and with the morphological amelioration of infected tissues. Scanning and transmission electron microscopy analyses indicated that the cytoplasm shrink of bacterial cells led to noticeable gaps between the cell membrane and cell cytoplasm, and the severely damaged cell membrane resulted in leakage of intracellular content, which ultimately caused the lethal effect of K-6 on bacteria. These findings demonstrated that K-6 is a potential agent against MRSA and MRSE.

Cholinesterase inhibitors from botanicals

Alzheimer's disease (AD) is a progressive neurodegenerative disease, wherein a progressive loss of cholinergic synapses occurs in hippocampus and neocortex. Decreased concentration of the neurotransmitter, acetylcholine (ACh), appears to be critical element in the development of dementia, and the most appropriate therapeutic approach to treat AD and other form of dementia is to restore acetylcholine levels by inhibiting both major form of cholinesterase: Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Consequently, researches have focused their attention towards finding cholinesterase inhibitors from natural products. A large number of such inhibitors have been isolated from medicinal plants. This review presents a comprehensive account of the advances in field of cholinesterase inhibitor phytoconstituents. The structures of some important phytoconstituents (collected through www.Chemspider.com) are also presented and the scope for future research is discussed.

The uniqueness and therapeutic value of natural products from West African medicinal plants. Part I: uniqueness and chemotaxonomy

This review gives an in depth coverage of the natural products derived from West African medicinal plants with diverse biological activities.

The uniqueness and therapeutic value of natural products from West African medicinal plants, part II: terpenoids, geographical distribution and drug discovery

In this review series, an attempt has been made to give indepth coverage of natural products derived from West African medicinal plants with diverse biological activities.

Natural AChE Inhibitors from Plants and their Contribution to Alzheimer's Disease Therapy

As acetylcholinesterase (AChE) inhibitors are an important therapeutic strategy in Alzheimer's disease, efforts are being made in search of new molecules with anti-AChE activity. The fact that naturally-occurring compounds from plants are considered to be a potential source of new inhibitors has led to the discovery of an important number of secondary metabolites and plant extracts with the ability of inhibiting the enzyme AChE, which, according to the cholinergic hypothesis, increases the levels of the neurotransmitter acetylcholine in the brain, thus improving cholinergic functions in patients with Alzheimer's disease and alleviating the symptoms of this neurological disorder. This review summarizes a total of 128 studies which correspond to the most relevant research work published during 2006-2012 (1st semester) on plant-derived compounds, plant extracts and essential oils found to elicit AChE inhibition.

Alkaloids from Pachysandra terminalis inhibit breast cancer invasion and have potential for development as antimetastasis therapeutic agents

The aim of the present study was to identify potentially useful natural compounds for the development of novel therapeutic agents to inhibit metastasis. A phytochemical investigation of Pachysandra terminalis resulted in the isolation of seven new pregnane alkaloids, terminamines A-G (1-7), and seven known alkaloids (8-14). The structures of 1-7 were elucidated by 1D- and 2D-NMR spectroscopic and mass spectrometric methods. Compounds 1-5 and 8-14 inhibited the migration of MB-MDA-231 breast cancer cells induced by the chemokine epithelial growth factor. In addition, compound 1 inhibited phosphorylation of integrin β(1), which plays an important role in MB-MDA-231 cell adhesion and metastasis.

Triterpenoid alkaloid derivatives from Buxus rugulosa

Four new triterpenoid alkaloid derivatives, buxrugulines A–D (1–4 ), together with four known ones (5–8 ), were isolated from the leaves and stems of Buxus rugulosa . The structures of compounds 1–4 were elucidated by NMR and MS spectroscopic analysis. All compounds were assayed for their cytotoxicities against HL-60, SMMC-7721, A549, MCF-7, and SW480 cells lines.

Terpenoid-Alkaloids: Their Biosynthetic Twist of Fate and Total Synthesis

Terpenes and alkaloids are ever-growing classes of natural products that provide new molecular structures which inspire chemists and possess a broad range of biological activity. Terpenoid-alkaloids originate from the same prenyl units that construct terpene skeletons. However, during biosynthesis, a nitrogen atom (or atoms) is introduced in the form of β-aminoethanol, ethylamine, or methylamine. Nitrogen incorporation can occur either before, during, or after the cyclase phase. The outcome of this unique biosynthesis is the formation of natural products containing unprecedented structures. These complex structural motifs expose current limitations in organic chemistry, thus providing opportunities for invention. This review focuses on total syntheses of terpenoid-alkaloids and unique issues presented by this class of natural products. More specifically, it examines how these syntheses relate to the way terpenoid-alkaloids are made in Nature. Developments in chemistry that have facilitated these syntheses are emphasized, as well as chemical technology needed to conquer those that evade synthesis.

Unexpected presence of graminan- and levan-type fructans in the evergreen frost-hardy eudicot Pachysandra terminalis (Buxaceae): purification, cloning, and functional analysis of a 6-SST/6-SFT enzyme

About 15% of flowering plants accumulate fructans. Inulin-type fructans with β(2,1) fructosyl linkages typically accumulate in the core eudicot families (e.g. Asteraceae), while levan-type fructans with β(2,6) linkages and branched, graminan-type fructans with mixed linkages predominate in monocot families. Here, we describe the unexpected finding that graminan- and levan-type fructans, as typically occurring in wheat (Triticum aestivum) and barley (Hordeum vulgare), also accumulate in Pachysandra terminalis, an evergreen, frost-hardy basal eudicot species. Part of the complex graminan- and levan-type fructans as accumulating in vivo can be produced in vitro by a sucrose:fructan 6-fructosyltransferase (6-SFT) enzyme with inherent sucrose:sucrose 1-fructosyltransferase (1-SST) and fructan 6-exohydrolase side activities. This enzyme produces a series of cereal-like graminan- and levan-type fructans from sucrose as a single substrate. The 6-SST/6-SFT enzyme was fully purified by classic column chromatography. In-gel trypsin digestion led to reverse transcription-polymerase chain reaction-based cDNA cloning. The functionality of the 6-SST/6-SFT cDNA was demonstrated after heterologous expression in Pichia pastoris. Both the recombinant and native enzymes showed rather similar substrate specificity characteristics, including peculiar temperature-dependent inherent 1-SST and fructan 6-exohydrolase side activities. The finding that cereal-type fructans accumulate in a basal eudicot species further confirms the polyphyletic origin of fructan biosynthesis in nature. Our data suggest that the fructan syndrome in P. terminalis can be considered as a recent evolutionary event. Putative connections between abiotic stress and fructans are discussed.

Natural products as a source of Alzheimer's drug leads

This review focuses on recent developments in the use of natural products as therapeutics for Alzheimer's disease. The compounds span a diverse array of structural classes and are organized according to their mechanism of action, with the focus primarily on the major hypotheses. Overall, the review discusses more than 180 compounds and summarizes 400 references.

Triterpenoid alkaloids from Buxus microphylla

Two new triterpenoid alkaloids, buxmicrophyllines J and K (1 and 2, resp.), together with four analogues, 3-6, were isolated from the leaves and stems of Buxus microphylla. The structures of the new compounds were elucidated by NMR and MS spectroscopic analyses. The partial assignments of the NMR spectra of 3 were also revised. Compounds 1 and 3-6 were evaluated for their growth inhibitory activity against human cell lines HL-60, SMMC-7721, A-549, SK-BR-3, and PANC-1. Compound 6 showed significant cytotoxicity against HL-60, SK-BR-3, and PANC-1 cell lines, with IC(50) values of 6.46, 19.61, and 28.57 microM, respectively.

Bioactive 5alpha-pregnane-type steroidal alkaloids from Sarcococca hookeriana

The bioassay-guided phytochemical investigation of Sarcococca hookeriana with respect to cholinesterase inhibitory properties has yielded two new 5alpha-pregnane-type steroidal alkaloids, hookerianamides J (1) and K (2), along with eight known compounds (3-10). The structures of 1 and 2 were elucidated by spectroscopic methods. These compounds displayed good to moderate activities in vitro against the enzymes acetylcholinesterase (IC 50 8.1-48.5 microM) and butyrylcholinesterase (IC 50 0.4-4.0 microM). Compounds 1-10 were also tested in vitro for their leishmanicidal activity against Leishmania major and for their antibacterial activities against Bacillus subtilis, Micrococcus luteus, Streptococcus faecalis, and Pseudomonas pallida.