Pittosporumxanthins, cycloaddition products of carotenoids with alpha-tocopherol from seeds of Pittosporum tobira

A series of carotenoid-alpha-tocopherol cycloaddition products, named pittosporumxanthins B1 ( 3), B2 ( 4), C1 ( 5), C2 ( 6), A3 ( 7), and A4 ( 8), were isolated from the seeds of Pittosporum tobira. The structures were determined to be cycloaddition products of 9' Z-antheraxanthin at the 11' and 12' positions with alpha-tocopherol ( 3 and 4), 9' Z-neoaxanthin with alpha-tocopherol ( 5 and 6), and 9 Z-violaxanthin with alpha-tocopherol ( 7 and 8) on the basis of a detailed analyses of MS and NMR spectroscopic data. The configurations of the carotenoid end groups in the pittosporumxanthins were determined by a modified Mosher's method. Compounds 3, 5, and 7 were assigned (11' R,12' S) and 4, 6, and 8 (11' S,12' R) absolute configurations using CD measurements.     

Cytotoxic principles from the sap of Kalmia latifolia

Examination of the sap of Kalmia latifolia has revealed Grayanotoxin I (1), phloretin (3), and 2',6'-dihydroxy-4-methoxyacetophenone (5) as cytotoxic components. Twenty-one dihydrochalcones have been synthesized and tested for cytotoxic activity. 2'3,3'4,4'-Pentahydroxydihydrochalcone (8) has been found to be cytotoxic and to have marginal activity in vivo. Seven new dihydrochalcones are described.     

Carotenoids of tunicates. III. The structural elucidation of two new marine carotenoids, amarouciaxanthin A and B

The structure of two new marine carotenoids, isolated from the tunicate, Amaroucium pliciferum, and designated as amarouciaxanthin A and B, were determined on the basis of chemical and spectral data. Amarouciaxanthin A was determined as (6S, 3'S, 5'R,6'R)- 6,3',5'-trihydroxy-4,5,6',7'-tetradehydro-7,8,5',6'-tetrahydro-beta, beta-carotene-3,8-dione, and Amarouciaxanthin B was determined as (6S,3'R)-6,3'-dihydroxy-4,5,7',8'-tetradehydro-7,8-dihydro-beta,beta- carotene-3,8-dione. These two compounds are also presumed to be new metabolic products of a typical marine carotenoid, fucoxanthin.     

New cytotoxic bis 5-alkylresorcinol derivatives from the leaves of Oncostemon bojerianum from the Madagascar rainforest

Bioassay-directed fractionation of a CH(2)Cl(2)-MeOH extract of the leaves of Oncostemon bojerianum resulted in the isolation of eight new 5-alkylresorcinols, named oncostemonols A-H (1-8), and two known derivatives, (8'Z)-1,3-dihydroxy-5-[16'-(3' ',5' '-dihydroxyphenyl)-8'-hexadecen-1'-yl]benzene (9) and (8'Z)-1,3-dihydroxy-5-[14'-(3' ',5' '-dihydroxyphenyl)-8'-tetradecen-1'-yl]benzene (10). The structures of the new compounds 1-8 were elucidated on the basis of extensive 1D and 2D NMR spectroscopic interpretation and chemical derivatization. All the compounds exhibited cytotoxic activity against the A2780 ovarian cancer cell line.     

Antioxidative and cytotoxic compounds extracted from the sap of Rhus succedanea

Two new antioxidative and cytotoxic compounds, 10'(Z),13'(E),15'(E)-heptadecatrienylhydroquinone (1) and 10'(Z),13'(E)-heptadecadienylhydroquinone (2), as well as the known 10'(Z)-heptadecenylhydroquinone (3), were isolated from an EtOH extract of the sap of Rhus succedanea. The structures were elucidated by spectral analyses. These compounds showed antioxidative and cytotoxic activities against five cancer cell lines.     

Plant anticancer agents. IX. Constituents of Hyptis tomentosa

The twigs, leaves, and flowers of Hyptis tomentosa were found to owe their major cytotoxic activity to the presence of desoxypodophyllotoxin (4), but the two weakly cytotoxic flavones 5-hydroxy-4',6,7,8-tetramethoxy flavone (3) and 5-hydroxy-4',3,6,7,8-pentamethoxy flavone (2) also contributed to the total cytotoxicity of the crude extracts. The flavones eupatorin (6) and 5-hydroxy-3',4',6,7-tetramethoxy flavone (5) were isolated as inactive constituents, together with the lignan sesamin (1).     

Stereoselective synthesis by olefin metathesis and characterization of η-carotene (7,8,7',8'-tetrahydro-β,β-carotene)

The purported structure of the elusive η-carotene (7,8,7',8'-tetrahydro-β,β-carotene), a natural C(40) carotenoid first detected in the berries of Lonicera japonica and in citrus fruits sixty years ago, has been synthesized by olefin cross-metathesis/dimerization of a C(21) polyene derived from trans-7,8-dihydroretinal, thus allowing the full characterization of this highly unstable natural product.     

New C(40)-carotenoid acyl glycoside as principal carotenoid in Salinibacter ruber,an extremely halophilic eubacterium

The principal (>96% of total) carotenoid in the novel, extremely halophilic eubacterium Salinibacter ruber, here called salinixanthin (1), has been assigned the structure (all-E,2'S)-2'-hydroxy-1'-[6-O-(13-methyltetradecanoyl)-beta-D-glycopyranosyloxy]-3',4'-didehydro-1',2'-dihydro-beta,psi-caroten-4-one by spectrometric (vis, EIMS, (1)HNMR, CD, GCMS) and chemical methods.     

Isolation of stereoisomeric epoxy carotenoids and new acetylenic carotenoid from the common freshwater goby Rhinogobius brunneus

Stereoisomeric epoxy carotenoids with 3,5-cis configuration, diadinoxanthin B [(3S,5S,6R,3'R)-diadinoxanthin] (1) and antheraxanthin B [(3S,5S,6R,3'R)-antheraxanthin] (2), along with diadinoxanthin A [(3S,5R,6S,3'R)-diadinoxanthin] and antheraxanthin A [(3S,5R,6S,3'R)-antheraxanthin], were isolated from the common freshwater goby Rhinogobius brunneus. This is the first example in nature of 3,5-cis carotenoid epoxides. Furthermore, a new acetylenic triol carotenoid, gobiusxanthin (3), was obtained, and its structure was determined to be 7,8-didehydro-beta, epsilon-carotene-3,3', 6'-triol by chemical and spectral data.     

Cytotoxic flavonoids from Platymiscium floribundum

Two new isoflavonoids, 7-hydroxy-6,4'-dimethoxy-isoflavonequinone (1) and 2'-hydroxy-6,4',6' ',4' '-tetramethoxy-[7-O-7' ']-bisisoflavone (2), and seven other known flavonoids, 3-hydroxy-9-methoxypterocarpan (medicarpin), 3,10-dihydroxy-9-methoxypterocarpan, 3,9-dimethoxypterocarpan (homopterocarpin) (3), 2,3,9-trimethoxypterocarpan (4), 3,4-dihydroxy-9-methoxypterocarpan (vesticarpan) (5), 2',4,4'-trihydroxychalcone (isoliquiritigenin), and 7,4'-dihydroxyflavanone (liquiritigenin) (6), were isolated from the heartwood of Platymiscium floribundum. The structures of compounds 1 and 2 were established by spectroscopic methods. Compounds 3-6 showed cytotoxic activity when evaluated against five human cancer cell lines in vitro.