Ping Yao

Rubesanolides A and B: Diterpenoids from Isodon rubescens

From the medicinal plant Isodon rubescens, we isolated two novel diterpenes, rubesanolides A (1) and B (2). The compounds contain a unique β-lactone subgroup. This is the first discovery for a natural diterpene having rings A, B, and C in chair, boat, and twist-chair conformations, respectively. The structures were elucidated by analysis of spectroscopic data, and the absolute configuration of 1 was determined by X-ray diffraction.

Novel taxoids from the Chinese yew Taxus yunnanensis

Six new taxoids, taxuyunnanines W (1), X (2), Y (3), Z (5), 10-deacetyl-10-(beta-glucopyranosyl)-yunnanxane (8), and 7-(beta-xylosyl)-N-methyl-taxol C (10), as well as taxuchin B (4) and yunnanxane (7), have been isolated from the bark of Taxus yunnanensis. Compounds 1 and 2 were characterized as 11 (15-->1)-abeo taxoids containing an orthoester group, which have not been reported from any Taxus plants to date; isolates 3 and 5 are the examples of taxanes having a tetrahydronfuran ring, being reported only for the second time; and 8 is the first natural 6/8/6 skeletal type taxane glucosidic form. This is also the first report of a co-occurrence of xylosidation and N-methylation in a taxane (10). Compound 4 is the only known chlorine-containing taxane found in nature thus far, and is being reported from this plant for the first time. The structures were determined by spectroscopic and chemical means including 1D and 2D NMR spectra

Taxane diterpenoids from the bark of Taxus yunnanensis.

Further investigation on the alcohol extract of the barks of Taxus yunnanensis led to the isolation of four taxoids, namely, 7beta-xylosyl-taxol D, taxuyunnanines P, Q and R, along with the known taxuyuntin G (2). Four are rearranged taxoids with an 11(15-->1)-abeotaxoid skeleton and an opened oxetane ring moiety. Structures were determined by spectroscopic and chemical means.

Non-taxane compounds from the bark of Taxus yunnanensis

From the bark of Taxus yunnanensis , 15 non-taxane compounds were isolated. Through spectroscopic methods such as 1D and 2D NMR and MS experiments, one of them was determined as a new abietane-type diterpenoid named taxayunnin ( 1 ). The other 14 known compounds were identified as taxamairin C ( 2 ), taxamairin A ( 3 ), 3 g -hydroxy-sandaracopimaric acid ( 4 ), (+)-3-hydroxy-isodrimenin ( 5 ), rubrosterone ( 6 ), ponasterone A ( 7 ), ecdysterone ( 8 ), 20-hydroxy-echysone-20,22-monoacetonide ( 9 ), 7-oxositosterol ( 10 ), stigmast-4-en-6 g -ol-3-one ( 11 ), 5 f ,6 g -dihydroxy-daucosterol ( 12 ), g -sitosterol ( 13 ), daucosterol ( 14 ), 1- O - g - d -glucopyranosyl-(2 S , 3 R , 4 E , 8 Z )-2- N -(2-hydroxypalmitoyl)-octadeca-sphinga-4,8-dienine ( 15 ), respectively. Compounds 4 - 6 , 9 - 12 and 15 were isolated from Taxus plants for the first time.

Compounds from the Fruits of the Popular European Medicinal Plant Vitex agnus-castus in Chemoprevention via NADP(H):Quinone Oxidoreductase Type 1 Induction

As part of our continuing efforts in the search for potential biologically active compounds from medicinal plants, we have isolated 18 compounds including two novel nitrogen containing diterpenes from extracts of the fruits of Vitex agnus-castus. These isolates, along with our previously obtained novel compound vitexlactam A (1), were evaluated for potential biological effects, including cancer chemoprevention. Chemically, the nitrogenous isolates were found to be two labdane diterpene alkaloids, each containing an α, β-unsaturated γ-lactam moiety. Structurally, they were elucidated to be 9α-hydroxy-13(14)-labden-16,15-amide (2) and 6β-acetoxy-9α-hydroxy-13(14)-labden-15,16-amide (3), which were named vitexlactams B and C, respectively. The 15 known isolates were identified as vitexilactone (4), rotundifuran (5), 8-epi-manoyl oxide (6), vitetrifolin D (7), spathulenol (8), cis-dihydro-dehydro-diconiferylalcohol-9-O-β-D-glucoside (9), luteolin-7-O-glucoside (10), 5-hydroxy-3,6,7,4′-tetramethoxyflavone (11), casticin (12), artemetin (13), aucubin (14), agnuside (15), β-sitosterol (16), p-hydroxybenzoic acid (17), and p-hydroxybenzoic acid glucose ester (18). All compound structures were determined/identified on the basis of 1D and/or 2D NMR and mass spectrometry techniques. Compounds 6, 8, 9, and 18 were reported from a Vitex spieces for the first time. The cancer chemopreventive potentials of these isolates were evaluated for NADP(H):quinone oxidoreductase type 1 (QR1) induction activity. Compound 7 demonstrated promising QR1 induction effect, while the new compound vitexlactam (3) was only slightly active.