Octanorcucurbitane triterpenoids protect against tert-butyl hydroperoxide-induced hepatotoxicity from the stems of Momordica charantia

Asymmetric De Novo Synthesis of a Cucurbitane Triterpenoid: Total Synthesis of Octanorcucurbitacin B

The asymmetric de novo synthesis of a cucurbitane natural product, octanorcucurbitacin B, has been accomplished. Cucurbitanes are a family of structurally complex triterpenoids that characteristically contain three stereodefined quaternary centers at ring fusion carbons positioned about their tetracyclic skeletons (at positions 9, 13, and 14). Taking a diversion from the biosynthetic hypothesis for cucurbitane synthesis, the approach established here provides direct access to the cucurbitane skeleton without having to proceed by way of a lanostane. Using a simple chiral enyne as starting material, a sequence of annulative cross-coupling and intramolecular Heck reaction provides a stereodefined polyunsaturated tetracycle possessing the C9 and C13 quaternary centers. This intermediate was converted to octanorcucurbitacin B through a 12-step sequence that features hydroxy-directed Simmons-Smith cyclopropanation, regioselective deconjugative alkylation, and allylic oxidation.

Jayaprakasha G, S. Patil B. Anti-Inflammatory, Antidiabetic Properties and In Silico Modeling of Cucurbitane-Type Triterpene Glycosides from Fruits of an Indian Cultivar of Momordica charantia L

Diabetes mellitus is a chronic disease and one of the fastest-growing health challenges of the last decades. Studies have shown that chronic low-grade inflammation and activation of the innate immune system are intimately involved in type 2 diabetes pathogenesis. Momordica charantia L. fruits are used in traditional medicine to manage diabetes. Herein, we report the purification of a new 23-O-β-d-allopyranosyl-5β,19-epoxycucurbitane-6,24-diene triterpene (charantoside XV, 6) along with 25ξ-isopropenylchole-5(6)-ene-3-O-β-d-glucopyranoside (1), karaviloside VI (2), karaviloside VIII (3), momordicoside L (4), momordicoside A (5) and kuguaglycoside C (7) from an Indian cultivar of Momordica charantia. At 50 µM compounds, 2–6 differentially affected the expression of pro-inflammatory markers IL-6, TNF-α, and iNOS, and mitochondrial marker COX-2. Compounds tested for the inhibition of α-amylase and α-glucosidase enzymes at 0.87 mM and 1.33 mM, respectively. Compounds showed similar α-amylase inhibitory activity than acarbose (0.13 mM) of control (68.0–76.6%). Karaviloside VIII (56.5%) was the most active compound in the α-glucosidase assay, followed by karaviloside VI (40.3%), while momordicoside L (23.7%), A (33.5%), and charantoside XV (23.9%) were the least active compounds. To better understand the mode of binding of cucurbitane-triterpenes to these enzymes, in silico docking of the isolated compounds was evaluated with α-amylase and α-glucosidase.

Cucurbitane-Type Triterpenoids from the Vines of Momordica charantia and Their Anti-inflammatory Activities

Seven new cucurbitane-type triterpenoids, kuguaovins A-G (1-7), and five known ones were isolated from the rattans of wild Momordica charantia. Their structures were established by spectroscopic data analyses, including 1D and 2D NMR, IR, and MS techniques. The absolute configurations of the cucurbitanes were determined from NOESY data and partially by X-ray crystallographic analysis. In pharmacological studies, compounds 1-7 and 9-12 exhibited weak anti-inflammatory effects (IC50 = 15-35 μM), based on an anti-NO production assay.

New Norcucurbitane Triterpenoids from Momordica charantia var. abbreviata

Two new 27-norcucurbitane triterpenoids, 5β,19-epoxy-3β-hydroxy-19( S)-methoxy-27-norcucurbita-6,23( E)-dien-25-one (1) and 3β-hydroxy-25-oxo-27-norcucurbita-6,23( E)-dien-5β,19-olide (2), together with one known cucurbitane triterpene, 5β,19-epoxycucurbita-6,23( E)-diene-3β,25-diol (3), were isolated from the fruits of Momordica charantia var. abbreviata. Their structures were elucidated by spectroscopic methods including EI-MS, 1H, 13C, and 2D NMR data and comparison with the data of known analogues.

Cucurbitane-Type Triterpenoids from Momordica charantia

Two new cucurbitane-type triterpenoids, 7β,23( S)-dimethoxycucurbita-5,24-dien-3β-ol (1) and 3 β-hydroxycucurbita-6,23( E),25-trien-5 β,19-olide (2), and two known cucurbitane-type triterpenoids, 7 β,25-dimethoxycucurbita-5,23( E)-dien-3 β-ol (3) and karavilagenin D (4), were isolated from the fruit pulp of Momordica charantia. Their structures were established by means of 1D and 2D NMR spectra (1H, 13C, COSY, HMQC, HMBC, and NOESY) as well as EI-MS data.

Bitter melon: a panacea for inflammation and cancer

Nature is a rich source of medicinal plants and their products that are useful for treatment of various diseases and disorders. Momordica charantia, commonly known as bitter melon or bitter gourd, is one of such plants known for its biological activities used in traditional system of medicines. This plant is cultivated in all over the world, including tropical areas of Asia, Amazon, east Africa, and the Caribbean and used as a vegetable as well as folk medicine. All parts of the plant, including the fruit, are commonly consumed and cooked with different vegetables, stir-fried, stuffed or used in small quantities in soups or beans to give a slightly bitter flavor and taste. The plant is reported to possess anti-oxidant, anti-inflammatory, anti-cancer, anti-diabetic, anti-bacterial, anti-obesity, and immunomodulatory activities. The plant extract inhibits cancer cell growth by inducing apoptosis, cell cycle arrest, autophagy and inhibiting cancer stem cells. The plant is rich in bioactive chemical constituents like cucurbitane type triterpenoids, triterpene glycosides, phenolic acids, flavonoids, essential oils, saponins, fatty acids, and proteins. Some of the isolated compounds (Kuguacin J, Karaviloside XI, Kuguaglycoside C, Momordicoside Q-U, Charantin, α-eleostearic acid) and proteins (α-Momorcharin, RNase MC2, MAP30) possess potent biological activity. In the present review, we are summarizing the anti-oxidant, anti-inflammatory, and anti-cancer activities of Momordica charantia along with a short account of important chemical constituents, providing a basis for establishing detail biological activities of the plant and developing novel drug molecules based on the active chemical constituents.

Cucurbitane-Type Triterpenoids from the Fruit Pulp of Momordica Charantia

Three new cucurbitane-type triterpenoids, 5β,19-epoxy-23(R)-methoxycucurbita-6,24-dien-3β-ol (1), 5β,19-epoxy-23(S)-methoxycucurbita-6,24-dien-3β-ol (2), and 3β-hydroxy-23(R)-methoxycucurbita-6,24-dien-5β,19-olide (3), were isolated from the fruit pulp of Momordica charantia. Their structures were established on the basis of extensive NMR (1H, 13C, COSY, HMQC, HMBC, and NOESY) and EI-MS studies. Compound 1 exhibited cytotoxic activity against the SK-Hep 1 cell line.

Cucurbitane triterpenoids from the leaves of Momordica charantia, and their cancer chemopreventive effects and cytotoxicities

Seventeen cucurbitane-type triterpenoids, 1-17, including six new compounds, (23E)-3β,25-dihydroxy-7β-methoxycucurbita-5,23-dien-19-al (1), (23S*)-3β-hydroxy-7β,23-dimethoxycucurbita-5,24-dien-19-al (6), (23R*)-23-O-methylmomordicine IV (7), (25ξ)-26-hydroxymomordicoside L (8), 25-oxo-27-normomordicoside L (9), and 25-O-methylkaravilagenin D (12), were isolated from a MeOH extract of the leaves of Japanese Momordica charantia. The structures of new compounds were elucidated on the basis of extensive spectroscopic analyses and comparison with literature. Compounds 1-17 were examined for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced with 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells, a known primary screening test for inhibitors of tumor promotion. Four compounds, 1, (23E)-3β,7β-dihydroxy-25-methoxycucurbita-5,23-dien-19-al (2), karavilagenin D (11), and 12, showed potent inhibitory effects on EBV-EA induction with IC(50) values in the range of 242-264 mol ratio/32 pmol TPA. In addition, compounds 1 and 11 exhibited inhibitory effects on skin-tumor promotion in an in vivo two-stage mouse skin carcinogenesis test based on 7,12-dimethylbenz[a]anthracene (DMBA) as initiator, and with TPA as a promoter. Furthermore, upon evaluation of the cytotoxic activities of compounds 1-17 against human cancer cell lines, compounds 2, 5-7, 9, and 14 showed potent activities against HL60 cell line, and compound 2 against SK-BR-3 cell line.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids, including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, serratanes and saponins; 305 references are cited.

Isolation and identification of cucurbitane-type triterpenoids with partial agonist/antagonist potential for estrogen receptors from Momordica charantia

This study aims at investigating the estrogenic activity and active cucurbitane-type triterpenoid compounds of bitter gourd (Momordica charantia, MC) using a transactivation assay for estrogen receptors (ER) α and β. The lyophilized fruits of MC were exhaustively extracted with ethyl acetate (EA) and 95% ethanol (EtOH), sequentially. The nonsaponifiable fraction (NS) of the EA extract as well as the acid hydrolyzed EtOH extract (AH) was fractionated and isolated by repeated column chromatography and further purified by preparative HPLC or RP-HPLC. One known compound, 5β,19-epoxycucurbita-6,24-diene-3β,23ξ-diol (6), was isolated from the NS, and five new compounds (1-5) were isolated from AH and identified as cucurbita-6,22(E),24-trien-3β-ol-19,5β-olide (1), 5β,19-epoxycucurbita-6,22(E),24-triene-3β,19-diol (2), 3β-hydroxycucurbita-5(10),6,22(E),24-tetraen-19-al (3), 19-dimethoxycucurbita-5(10),6,22(E),24-tetraen-3β-ol (4), and 19-nor-cucurbita-5(10),6,8,22(E),24-pentaen-3β-ol (5). In the noncytotoxic concentration range, compounds 1, 2, 5 and 6 showed weak agonistic activity via ER α and β. Compounds 1, 2, 3 and 6 significantly antagonized the transactvation of 17β-estradiol (E(2)) via both ER α and β. In conclusion, this study demonstrates, for the first time as far as we know, the partial agonist/antagonist activity via ER of four new and one known cucurbitane-type triterpenoids from MC. Further studies are worthy to explore the selective estrogen receptor modulator (SERM) activity of MC.

Carotenoid content and expression of phytoene synthase and phytoene desaturase genes in bitter melon (Momordica charantia)

Momordica charantia, a tropical plant, produces a fruit that has a β-carotene concentration five times higher than that of carrot. To elucidate the molecular basis of β-carotene accumulation in M. charantia, the gene expression levels of phytoene synthase (McPSY) and phytoene desaturase (McPDS) were determined. These levels were particularly high in the flowers of M. charantia. During fruit maturation, the expression levels of McPSY and McPDS decreased during the mid-stages but increased in the fully mature fruit. In addition, carotenoids accumulated as the peel changed from green to orange. Thus, McPSY and McPDS expression correlated with carotenoid accumulation during fruit maturation. Principal component analysis (PCA) also was used to evaluate the differences among the profiles of seven carotenoids identified in the fruit at several maturation stages. Riper fruits had higher carotenoid concentrations than less ripe fruits.