A Homodimer of Withaferin A Formed by Base-Promoted Elimination of Acetic Acid from 27-O-Acetylwithaferin A Followed by a Diels-Alder Reaction.

Treatment of 27-O-acetylwithaferin A (2) with the non-nucleophilic base, 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), afforded 5ß,6ß-epoxy-4ß-hydroxy-1-oxo-witha-2(3),23(24),25(27)-trienolide (3) and 4, a homodimer of withaferin A resulting from a Diels-Alder [4 + 2] type cycloaddition of the intermediate α,ß-dimethylene-δ-lactone (9). Structures of 3 and 4 were elucidated using HRMS and 1D and 2D NMR spectroscopic data. The structure of 4 was also confirmed by single crystal X-ray crystallographic analysis of its bis-4-O-p-nitrobenzoate (8). Formation of withaferin A homodimer (4) as the major product suggests regio- and stereoselectivity of the Diels-Alder [4 + 2] cycloaddition reaction of 9. Acetylation of 2-4 afforded their acetyl derivatives 5-7, respectively. Compounds 2-4 and 6-8 were evaluated for their cytotoxic activities against four prostate cancer (PC) cell lines (LNCaP, 22Rv1, DU-145, and PC-3) and normal human foreskin fibroblast (HFF) cells. Significantly, 4 exhibited improved activity compared to the other compounds for most of the tested cell lines.

Auto-oxidation of Ent-beyer-15-en-19-al isolated from the essential oil of the heartwood of Erythroxylum monogynum Roxb.: formation of 15,16-epoxy-ent-beyeran-19-oic acid and other products.

Chemical investigation of the essential oil obtained from the heartwood of Erythroxylum monogynum Roxb. yielded three beyerene type diterpenoids ent-beyer-15-ene (1), ent-beyer-15-en-19-ol (erythroxylol A) (2) and ent-beyer-15-en-19-al (3). Ent-beyer-15-en-19-al (3) was found to be unstable at room temperature, giving rise to hitherto unknown 15,16-epoxy-ent-beyeran-19-oic acid (4). This conversion involves the auto-oxidation of a C-4 axial aldehyde group of an ent-beyer-15-ene diterpenoid with the concurrent epoxidation of the C-15 double bond. This is the first report of the auto-oxidation of an aldehyde group to a carboxylic acid group with the concurrent epoxidation of a double bond in the same compound. Further investigation of this observation under controlled conditions resulted in the isolation and identification of ent-beyer-15-en-19-oic acid (5), two new epoxy hydroperoxides, 15,16-epoxy-19-nor-ent-beyeran-4α-hydroperoxide (6a), 15,16-epoxy-18-nor-ent-beyeran-4ß-hydroperoxide (6b), and two new hydroperoxides, ent-beyer-19-nor-15-en-4α-hydroperoxide (7), ent-beyer-18-nor-15-en-4ß-hydroperoxide (8) and ent-beyer-18-nor-15-en-4ß-ol (9). Identification of these compounds was carried out by the extensive usage of spectroscopic data including 1D and 2D NMR. The acid 5 and the alcohol 9 have been reported previously as natural products from Elaeoselinum asclepium and Erythroxylum monogynum. The mechanistic basis of this auto-oxidation reaction is discussed.

Potent antibacterial, antioxidant and toxic activities of extracts from Passiflora suberosa L. leaves.

Passiflora suberosa L. belonging to the family Passifloraceae is an important medicinal plant used in traditional medicinal system in Sri Lanka to treat diabetes, hypertension and skin diseases. We extracted P. suberosa leaves under reflux conditions using different solvents (hexane, chloroform, methanol and water), then subjected to phytochemical screening. Alkaloids, flavonoids and saponins and saponins and anthraquinones were present in hexane and chloroform extracts. Alkaloids, unsaturated sterols, triterpenes, saponins, flavonoids and tannins were observed in both methanol and aqueous extracts. Proanthocyanidins were observed only in the aqueous extract. Hence, aqueous and methanol extracts with most classes of phytochemicals present were subjected to antimicrobial, antioxidant, antihaemolytic activities and Brine shrimp lethality studies. Antibacterial activity and minimum inhibition concentrations were evaluated using three Gram-positive (Bacillus subtilis, Staphylococcus aureus and Enterococcus faecium) and three Gram-negative bacteria (Pseudumonas aeruginosa, Salmonella typhimuriam and Escherichia coli). The results indicated that only the methanol extract of P. suberosa exhibited antibacterial activities against all the strains of Gram-negative and Gram-positive bacterial with stronger activity against Gram-negative bacteria. DPHH (2,2-diphenyl-1-picrylhydrazy) scavenging assay was adopted to evaluate antioxidant properties while antihaemolytic and toxic activities were studied respectively using cow blood and Brine shrimp lethality assay. The IC50 values of the aqueous extract in both antioxidant and antihaemolytic assays were significantly lower than the standard ascorbic acid. Similar results were observed in the Brine shrimp lethality assay. In conclusion both aqueous and methanol extracts of P. suberosa leaves showed the presence of majority of phytochemicals including proanthocyanidins. Antibacterial activity was obtained only for methanol extract with better activity against Gram-negative bacteria. The aqueous extract showed better antioxidant, antihaemolytic and toxic activities than the methanol extract and their respective standards. Further investigations on the chemical composition and possible isolation of active ingredients is warranted.

Cytotoxic and Noncytotoxic Metabolites from Teratosphaeria sp. FL2137, a Fungus Associated with Pinus clausa.

A new naphthoquinone, teratosphaerone A (1), four new naphthalenones, namely, teratosphaerone B (2), structurally related to 1, iso-balticol B (3), iso-balticol B-4,9-acetonide (4), and (+)-balticol C (5), a new furanonaphthalenone, (3a S,9 R,9a S)-1(9a),3(3a),9-hexahydromonosporascone (6), and the known metabolite monosporascone (7) were isolated from Teratosphaeria sp. FL2137, a fungal strain inhabiting the internal tissue of recently dead but undecomposed foliage of Pinus clausa. The structures of 1-6 were elucidated on the basis of their spectroscopic data including 2D NMR, and absolute configurations of 2, 3, and 6 were determined by the modified Mosher's ester method. When evaluated in a panel of five tumor cell lines, metabolites 1 and 7 isolated from a cytotoxic fraction of the extract exhibited moderate selectivity for metastatic breast adenocarcinoma cell line MDA-MB-231. Of these, 1 showed cytotoxicity to this cell line with an IC50 of 1.2 ± 0.1 µM.

In vitro antioxidant, anti-inflammatory and anticancer activities of ethyl acetate soluble proanthocyanidins of the inflorescence of Cocos nucifera L.

BACKGROUND: Proanthocyanidins belong to a class of polyphenolic compounds called flavonoids and have been reported to exhibit important biological activities. The immature inflorescence of Cocos nucifera L. is used by Ayurvedic and traditional medical practitioners for the treatment of menorrhagia in Sri Lanka. Our studies have shown that the inflorescence of Cocos nucifera L. predominantly contains proanthocyanidins. OBJECTIVE: To determine the antioxidant, anti-inflammatory and anticancer activities of ethyl acetate soluble proanthocyanidins (EASPA) of immature inflorescence of Cocos nucifera L. METHODS: EASPA fraction of an acetone/water (7:3) extract of Cocos nucifera L. inflorescence was purified on Sephadex LH-20 and was used for the study. Antioxidant activity of EASPA was determined using DPPH and SOR scavenging assays. Anti-inflammatory activity of EASPA was determined by oxidative burst assay using chemiluminescence technique. MTT colorimetric assay was used to evaluate the cytotoxicity of EASPA to both PC3 and HeLa cells. RESULTS: EASPA showed radical scavenging activity against both DPPH and superoxide radicals with IC50 values of 11.02 ± 0.60 µg/mL and 26.11 ± 0.72 µg/mL. In both assays, EASPA showed less antioxidant activity than the standards used. It exhibited similar anti-inflammatory activity (IC50 = 10.31 ± 1.11 µg/mL) to ibuprofen (IC50 = 11.20 ± 1.90 µg/mL) (P ≥ 0.05). EASPA also showed stronger cytotoxic activity towards Hela cells (IC50 = 18.78 ± 0.90 µg/mL) than tamoxifen (IC50 = 28.80 ± 1.94 µg/mL) (P ≤ 0.05), while low cytotoxicity was observed against PC3 cells (IC50 = 44.21 ± 0.73 µg/mL) compared to doxorubicin (IC50 = 1.38 ± 0.16 µg/mL). CONCLUSION: EASPA showed antioxidant, anti-inflammatory and anticancer activities.