Diarylheptanoid Glucosides from Pyrostria major and Their Antiprotozoal Activities

In vitro screening of natural product-based compounds for leishmanicidal activity

Leishmaniasis is one of the major parasitic diseases, caused by obligate intracellular protozoa Leishmania, having high mortality as well as morbidity rate. As there is no human licensed vaccine available against leishmaniasis, chemotherapy remains the major way of combating this disease. Many disadvantages are known to be associated with the current drug regime including severe side effects and toxicity, long duration and expensive treatment, and the emergence of resistance. An alternative approach is being utilized to search for active molecules using natural sources, rather than relying on synthetic drugs. Many plant-derived secondary metabolites like phenolic compounds, steroids, quinones, etc. are being extensively investigated for their anti-leishmanial potential. One such group of complex phenolic compounds are diarylheptanoids. These compounds have been shown to exhibit anti-inflammatory, anti-parasitic, anti-fungal, and other pharmacological activities. In the present study, a set of sixteen tetrahydropyran derivatives including three natural products were obtained in lyophilized form. These compounds with trans-2,6-disubstituted tetrahydropyrans, Diospongin A, Diospongin B (isolated from Dioscorea spongiosa) and Centrolobine (Centrolobium sclerophyllum) as parent compounds were synthesized by the reaction of 1-phenyl-1-triemthylsiloxyethylene with six-membered cyclic hemiacetals in the presence of iodine as a catalyst. All the sixteen synthesized tetrahydropyran derivatives were used for toxicity analysis against L. donovani promastigotes, amastigotes and THP-1-derived human macrophages. IC50 values and selectivity index were calculated for all the compounds. Out of these sixteen, five compounds showed the best effect in vitro in terms of both leishmanicidal activity and non-toxicity to human macrophages.

Anti-tumor activity and linear-diarylheptanoids of herbal couple Curcumae Rhizoma-Sparganii Rhizoma and the single herbs

ETHNOPHARMACOLOGICAL RELEVANCE

Curcumae Rhizoma and Sparganii Rhizoma (CR-SR) are the classical herbal couple for activating blood circulation and treating tumor in clinics.

AIM OF THE STUDY

To investigate the anti-tumor activity and to clarify the bioactive ingredients of herbal couple CR-SR and the single herbs Curcumae Rhizoma (CR) and Sparganii Rhizoma (SR).

MATERIALS AND METHODS

The active fractions of CR-SR decoction were fractioned by column chromatography. And isolated compounds were characterized by IR, ESI-MS, 1D and 2D-NMR techniques. Detecting linear-diarylheptanoids in CR-SR, CR and SR was realized through UPLC-LTQ-Orbitrap MSⁿ, based on the fragmentation pathways established in this study, comparison with MS data of isolated compounds and references. The anti-tumor activities of different solvent fractions from CR-SR, CR and SR, as well as isolated ingredients were tested by CCK-8 method.

RESULTS

Ultimately, a new compound (1), having a sulfonic acid group at C-3, named demethoxyshogasulfonic acid, along with another structurally similar 17 known linear-diarylheptanoids were isolated. These linear-diarylheptanoids (1-18) were divided into 12 categories based on the differences of substituents at C-3 and C-5 on the straight chain of seven carbons. Six fragmentation pathways were established by summarizing MS data of the 18 isolated compounds collected from UPLC-MS. Based on that, and retention times and MS fragmentation ions, 47 linear-diarylheptanoids were identified in CR-SR and CR, in which 12 linear-diarylheptanoids were also detected in SR. Most importantly, 5 sulfonated linear-diarylheptanoids were new compounds detected in CR and CR-SR. And the biological assay indicated that compounds 1-4 and 12-15 significantly reduced the proliferation and inhibited colony formation of MCF-7 and HepG2 cells.

CONCLUSION

The new compound (1) exhibited good anti-cancer activity, which suggests that a great effort has to be paid to investigate the bioactivity of sulfonated compounds. The fractions of CR-SR decoction exhibited stronger anti-tumor activities than that of CR and SR against 5 different cancer cells. As for chemical composition, it is the first time to report that diarylheptanoids are in Sparganiaceae and the sulfonated compounds in Zingiberaceae. Moreover, the linear-diarylheptanoids found in SR which being tested to possess good anti-tumor activity, plus those compounds in CR enhance the capacity of CR-SR. It shows importance of TCM compatibility.

Diarylheptanoids as nutraceutical: A review

Phenolic compounds are naturally occurring compounds present ubiquitously in plants. They have potential health benefits and substantiate evidence for their nutraceutical applications. Diarylheptanoids are part of the broad class of plant phenolics with structurally divergent compounds. They have been used in traditional medicines and homemade remedies to treat various ailments, as organoleptic additives in foods, and also for aesthetic purposes. With their potential therapeutic and organoleptic characteristics, diarylhepatanoids can be rightly termed as nutraceuticals. This review summarizes the wide range of pharmacological activities of diarylhepatanoids and nutraceutical formulations, with relevance to human health.

Characterization of diarylheptanoids: An emerging class of bioactive natural products

Diarylheptanoids are a class of secondary plant metabolites with a wide variety of bioactivity. Research on their phytochemistry and phytoanalysis is rapidly growing and the number of identified structures bearing the aryl-C₇-aryl skeleton is at present approaching 500. Historically, the yellow pigment curcumin has been characterized as the first diarylheptanoid and the extensive research on naturally occurring analogues is still ongoing. In this review, studies dealing with the characterization of linear and cyclic derivatives are discussed from the phytoanalytical point of view. Isolation, fractionation and purification strategies from natural sources along with their chromatographic behavior and structural characteristics are discussed. The role of various techniques used for the extraction (such as Soxhlet extraction, sonication, maceration/percolation, microwave-assisted extraction, supercritical carbon dioxide extraction); isolation (liquid-liquid extraction, column chromatographic techniques, preparative thin-layer and high-performance liquid chromatography, centrifugal partition chromatography, counter-current chromatography); separation (thin-layer chromatography, high-performance liquid chromatography, gas chromatography, capillary electrophoresis) and structural characterization (UV/Vis spectroscopy, infrared spectroscopy, X-ray crystallography, mass spectrometry, nuclear magnetic resonance spectroscopy and circular dichroism spectroscopy) are critically reviewed.

Revisiting Previously Investigated Plants: A Molecular Networking-Based Study of Geissospermum laeve

Three new monoterpene indole alkaloids (1-3) have been isolated from the bark of Geissospermum laeve, together with the known alkaloids (-)-leuconolam (4), geissolosimine (5), and geissospermine (6). The structures of 1-3 were elucidated by analysis of their HRMS and NMR spectroscopic data. The absolute configuration of geissolaevine (1) was deduced from the comparison of experimental and theoretically calculated ECD spectra. The isolation workflow was guided by a molecular networking-based dereplication strategy using an in-house database of monoterpene indole alkaloids. In addition, five known compounds previously undescribed in the Geissospermum genus were dereplicated from the G. laeve alkaloid extract network and were assigned with various levels of identification confidence. The antiparasitic activities against Plasmodium falciparum and Leishmania donovani as well as the cytotoxic activity against the MRC-5 cell line were determined for compounds 1-5.

Focus on PAINS: false friends in the quest for selective anti-protozoal lead structures from Nature?

Pan-assay interference compounds (PAINS) are molecules showing promising but deceptive activities in various biochemical screenings mainly due to unselective interactions with the target.

Anti-Trypanosomal Activity of Diarylheptanoids Isolated from the Bark ofAlnus japonica

The crude extract of Alnus japonica bark exhibited a strong effect on the growth of Trypanosoma brucei. Subsequent chromatographic separation resulted in the isolation of two novel diarylheptanoids, known as alnuside C (2) and alnuside D (3), and three known compounds, 1-(3,4-dihydroxyphenyl)-7-(4-hydroxyphenyl)-heptan-3(R)-O-β-D-glucopyranoside (1), oregonin (4) and hirsutanone (5). The structures of the isolates were elucidated based on the use of extensive spectroscopic and chemical methods. Among the isolated diarylheptanoids, oregonin (4) (a major component of plant bark) and hirsutanone (5) exhibited potent in vitro inhibitory activity against T. brucei growth in the bloodstream with IC50values of 1.14 and 1.78 μM, respectively. We confirmed that oregonin (4) and hirsutanone (5) were not toxic to human normal skin fibroblast cells (NB1RGB) and colon cancer cells (HCT-15) at a concentration of 50 μM; however, lower levels of toxicity were observed for leukemia cells. To determine the structure activity relationships of the isolated components, we performed Conformation Search and found that the 3-oxo function of the heptane chain in the diarylheptanoid molecule is required for their trypanocidal activity.

New Diarylheptanoids and a Hydroxylated Ottelione from Ottelia alismoides

Ten new diarylheptanoids (2, 3, 4, 5a-d, 6, 7, and 8) have been isolated from an extract of Ottelia alismoides. The structures of these previously unknown metabolites were determined by NMR spectroscopic analysis. A previously unknown, hydroxylated analog of the known otteliones A and B (1a and 1b)–namely, 3a-hydroxyottelione (13)–was also isolated. The 1H NMR analysis of the Mosher esters of alcohols derived from otteliones A and B (S-17/R-17 and S-20/R-20) are also reported.