反应详情

Sesquiterpene alcohols and ketones are an interesting group of compounds for a number of reasons. Sesquiterpene alcohols, for example have been shown to be involved in resistance against micro-organisms: the Solanaceae for example produce sesquiterpene alcohol phytoalexins upon infection with pathogenic fungi and in vitro assays have shown that these sequiterpene alcohols have a strong antifugal activity. Also a number of sesquiterpene alcohols are important in the flavor and fragrance industry, for example santalol, typical for the very expensive sandalwood essential oil, and khusimol, patchoulol, etc. Also the sesquiterpene ketone, nootkatone is a commercially important compound. Because of its excellent organoleptic qualities and in particular its typical grapefruit taste, nootkatone is a widely used ingredient in perfumery and the flavor industry. Nootkatone was also shown to inhibit gastric lesion which explains that it is a constituent of some stomach medications (Yamahara et al., 1990). Although nootkatone can be obtained from valencene or other substrates using chemical synthesis (Hunter and Brogden, 1965; Wilson and Shaw, 1978; Canadian patent no 901601; M. Pesaro et al., 1968; Birch, 1974; U.S. Pat. No. 5,847,226) there is a large demand for natural nootkatone. At present, such a quality can only be obtained by extraction of natural products containing nootkatone, in particular grapefruit, a method which is hardly economic. With the enzymes lignin peroxidase (from Phanerochaete chrysosporium) and lactoperoxidase it is possible to convert (+)-valencene into nootkatone under certain conditions. In this way, the conversion is very low and is most probably due to singlet oxygen that is formed by these two enzymes (Willershausen and Graf, 1991). Several microorganisms, bacteria and fungi, were also screened for their capability to transform (+)-valencene into nootkatone all without much success. (Balfoort, 1994). Two bacteria of the genus Enterobacter from a Dutch soil and an infected local beer were isolated by enrichment cultures on (+)-valencene. These bacteria transformed (+)-valencene into nootkatone (12% yield) and many other valencene derivatives (Dhavlikar and Albroscheit, 1973). Also other methods for the bioconversion of valencene to nootkatone using inicro-organisms have been studied, but none of these methods have proven commercially viable (Dhavlikar et al., 1973; Drawert et al., 1984).