[Chemical Constituents from Ethyl Acetate Extract of Psidium guajava Leaves (II)].

OBJECTIVE: To study the chemical constituents from ethyl acetate extract of Psidium guajava leaves. METHODS: The constituents were separated and purified by silica gel and Sephadex LH-20 column chromatography and their structures were identified on the basis of physicochemical properties and spectral data. RESULTS: Eleven compounds were isolated and identified as 6,10,14-trimethyl-2-pentadecanone (1), phytyl-acetate (2), cubenol (3), eucalyptin (4), n-docosanoic acid-p-hydroxy-phenethylol ester (5),8-methyl-5,7- dihydroxy-flavonone (6), 6-methyl-5,7-dihydroxy-flavonone (7), betulinic acid (8), carnosol (9), quercetin (10), and 2,4,6-tirhydroxy- 3,5-dimethyl-diphenylketone-4-O-(6'"-O-galloyl)-ß-D-glucoside (11). CONCLUSION: Compounds 1-9 are isolated from this plant for the first time.

Phytoecdysteroids from the roots of Achyranthes bidentata Blume.

Two new phytoecdysteroids, (25S)-20,22-O-(R-ethylidene)inokosterone and 20,22-O-(R-3-methoxycarbonyl)propylidene-20-hydroxyecdysone, together with six known phytoecdysteroids 3-8 were isolated from the roots of Achyranthes bidentata Blume. The new structures were established on the basis of spectroscopic studies and chemical evidences. The absolute configuration at C-25 in the structure of known compound 3 was determined by chemical and spectroscopic means.

[Studies on the chemical components and antibacterial activity of essential oil from the leaves of Rubus corchorifolius].

OBJECTIVE: To analyze the chemical components of essential oil from the leaves of Rubus corchorifolius. METHODS: The essential oil was extracted by steam distillation, and then an analysis was conducted by applying GC-MS and Xcalibur Software. K-B filter paper method was used for their bacteriostasish. RESULTS: 44 compounds were identified, accounting for 88.52% of the total essential oil. The volatile oil concentration of 50% had a good bactericidal effect and the concentration of 0.5% still had excellent antibacterial effect. CONCLUSION: It provides the foundation for reasonable utilization and development of the leaves of Rubus corchorifolius.

Novel skeleton sesquiterpenoids isolated from guava leaves.

A chemical investigation of the plant Psidium guajava L., collected in Guangdong province, afforded two novel skeleton sesquiterpenoids 1 and 2. Compound 2 also known as isocaryolan-9-one was a new natural product. The structure of the novel compound 1 was determined as guavacid A by various spectroscopic methods. A possible biosynthetic pathway for 1 and 2 was proposed.

Antibacterial oleanane-type triterpenoids from pericarps of Akebia trifoliata.

Three new oleanane triterpenoids, 2α,3ß,29-trihydroxyolean-12-en-28-oic acid (1), 2α,3ß-dihydroxy-23-oxo-olean-12-en-28-oic acid (2) and 2α,3ß,21ß,22α-tetrahydroxyolean-12-en-28,29-dioic acid (3), and ten known ones, maslinic acid (4), arjunolic acid (5), oleanolic acid (6), 3-epi-oleanolic acid (7), stachlic acid A (8), serratagenic acid (9), gypsogenic acid (10), 2α,3ß-dihydroxyol-ean-13(18)-en-28-oic acid (11), mesembryanthemoidigenic acid (12) and 12α-hydroxy-δ-lactone (13), were isolated from the pericarps of Akebia trifoliata, a new valued fruit crop in China. Their structures were elucidated on the basis of extensive spectroscopic analysis. Compounds 8, 10, 11 and 13 were isolated for the first time from the genus Akebia. All the compounds were tested for their antimicrobial activity against five bacterial strains. Compounds 4, 6 and 11 showed significant antibacterial activity toward all the assayed microorganisms with MIC values ranging from 0.9 to 15.6µg/mL, which were close or even more potent than the reference compound Kanamycin (MIC values ranging from 1.9 to 3.9µg/mL).