We continue to study the biotransformation of terpenoids and aromatic compounds from crude drugs, liverworts and animal origin by microorganisms [1][2][3][4][5][6][7][8] and mammals 9,10) to obtain functional substances such as pheromones, aromas, and insecticides. Recently, we succeeded in highly efficient production of nootkatone, the most important and expensive grapefruit aroma that decreases somatic fat ratio 11) from the cheap and commercially available valencane-type sesquiterpene hydrocarbon valencene (3) from the valencia orange oil, by biotransformation using Chlorella and Mucor species.
12-14)The structure of aristolane-type sesquiterpene, (ϩ)-1(10)-aristolene (ϭb-gurjunene) (1) 15) whose structure resembles that of nootkatone (4) except for the presence of a 1,1-dimethylcyclopropane ring in the molecule, 1(10)-aristolen-2-one (5) 16,17) possessing excellent citrus scent and anti-microbial activity, and 9a-hydroxy-1(10)-aristolen-2-one (ϭde-bilon) (6) 18,19) having cytotoxic activity were isolated from Nardostachys chinensis. (Ϫ)-Aristolone (7) 20) and 1(10)-aristolen-12-al (9), 21) which inhibit melanin synthesis, 22,23) were also isolated from Aristolochia debilis, while the enantiomer (8) of 7 was obtained from the liverworts Porella caespitans var. setigera 24,25) and Reboulia hemisphaerica.
26)We have previously reported the distribution of a number of novel terpenoids and aromatic compounds possessing biological activities such as antimicrobial, antitumor, and neural sprouting activities. 24,25) 2,3-Secoaromadendrane-type sesquiterpenoids such as plagiochilide (2) and plagiochiline A (10), which are distributed only in liverworts Plagiochila species, also possess a 1,1-dimethylcyclopropane ring. 24,25) Plagiochilide (2) elicits a nerve cell degeneration reparation activity, 27) and plagiochiline A (10) displays strong pungent tasting, intensive insect antifeedant and piscicidal acitivities. 24,25) To obtain more biologically active compounds than the original aristolanes and 2,3-secoaromadendranes, biotransformation of (ϩ)-1(10)-aristolene (1) and plagiochilide (2) by Chlorella fusca var. vacuolata, Mucor species, and Aspergillus niger was examined. This paper deals with the structure elucidation of metabolites obtained by biotransformation of 1 and 2 by these three microorganisms and their Yamashiro-cho, Tokushima 770-8514, Japan. Received January 30, 2006; accepted March 13, 2006 Biotransformation of the aristolane-type sesquiterpene hydrocarbon (؉)-1(10)-aristolene (1) from the crude drug Nardostachys chinensis and of the 2,3-secoaromadendrane-type sesquiterpene lactone plagiochilide (2) from the liverwort Plagiochila fruticosa by three microorganisms, Chlorella fusca var. vacuolata, Mucor species, and Aspergillus niger was investigated. C. fusca var. vacuolata and Mucor sp. introduced oxygen function into the cyclohexane ring of aristolene while A. niger oxidized stereoselectively one methyl of the 1,1-dimethyl group on the cyclopropane ring of aristolanes and 2,3-secoaromadendrane to gi...