Elsevier

Bioresource Technology

Volume 115, July 2012, Pages 70-74
Bioresource Technology

Transformation of (±)-lavandulol and (±)-tetrahydrolavandulol by a fungal strain Rhizopus oryzae

Dedicated to Dr. S. Sivaram, National Chemical Laboratory, Pune, on the occasion of his 65th birthday.
https://doi.org/10.1016/j.biortech.2011.11.038Get rights and content

Abstract

Biotransformation of an irregular monoterpene alcohol, (±)-lavandulol [(±)-5-methyl-2-(1-methylethenyl)-4-hexen-1-ol] (I) and its tetrahydro derivative, (±)-tetrahydrolavandulol [(±)-2-isopropyl-5-methylhexan-1-ol] (II) were studied using a soil isolated fungal strain Rhizopus oryzae. Five metabolites, 2-((3,3-dimethyloxiran-2-yl)methyl)-3-methylbut-3-en-1-ol (Ia), 2-methyl-5-(prop-1-en-2-yl)hex-2-ene-1,6-diol (Ib), 2-methyl-5-(prop-1-en-2-yl)hexane-1,6-diol (Ic), 2-(3-methylbut-2-enyl)-3-methylenebutane-1,4-diol (Id), 5-methyl-2-(2-methyloxiran-2-yl)hex-4-en-1-ol (Ie) have been isolated from the fermentation medium and characterized with lavandulol as a substrate. When tetrahydrolavandulol used as a substrate, two metabolites 2-isopropyl-5-methylhexane-1,5-diol (IIa) and 2-isopentyl-3-methylbutane-1,3-diol (IIb) have been isolated from the fermentation medium. Biotransformation studies with R. oryzae clearly indicate that the organism initiates the transformation either by hydroxylation at allylic methyl groups or epoxidation of double bond. GC and GCMS analyses indicated that both (R)- and (S)-enantiomers of I and II have been transformed into corresponding hydroxylated or epoxy derivatives, when racemic I and II were used as substrates.

Highlights

Biotransformation of lavandulol and tetrahydrolavandulol studied using Rhizopus oryzae. ► Five metabolites isolated and characterized with lavandulol. ► Two metabolites isolated and characterized with tetrahydrolavandulol. ► R. oryzae efficiently carried out hydroxylation and epoxidation.

Introduction

The irregular monoterpene alcohol, lavandulol is a constituent of essential oils and also an important additive in perfumery and cosmetic industry (Schinz and Schappi, 1947, Seino et al., 2008, Simon et al., 1946, Soucek and Dolejs, 1959). Homochiral lavandulol exists naturally in its (R)-form in the essential oil of lavender. The esters of both (R)- and (S)-lavandulol are the segregation pheromones of insects such as Anthonomus rubi Herbst (Innocenzi et al., 2001) and Planococcus ficus, (Zada et al., 2003, Zada et al., 2008), respectively. (R)-lavandulyl-(S)-methylbutanoate is a component of female sex pheromone of the hibiscus mealybug (Zhang et al., 2004) whereas (R)-lavandulyl acetate is a component of the male sex pheromone of the western flower thrips (Hamilton et al., 2005). (R)-lavandulol is being synthesized in nature by the condensation of two molecules of dimethylallyldiphosphate (DMAPP) and the mechanism of formation of (R)-lavandulol is well documented (SD, Fig. S1) (Thulasiram et al., 2007). 1′-2 Irregular monoterpene, (R)-lavandulol was formed through dissociative electrophilic alkylation of the double bond in DMAPP by the dimethylallyl carbocation (DMA+) to give cyclopropyl carbocation. The cyclopropyl carbocation formed after rearrangement yield lavandulyl carbocation which in turn will be deprotonated to yield lavandulyl diphosphate (SD, Fig. S1) (Thulasiram et al., 2007, Thulasiram et al., 2008). Although considerable work has been carried out on the biosynthesis of lavandulol, very little is known regarding the biotransformation of this irregular monoterpene alcohol. Therefore, it is of great interest to know the mode of biotransformation of lavandulol and tetrahydrolavandulol as they are being used extensively in perfumery and cosmetic industry. This study describes the biotransformation of racemic lavandulol (I) and its tetrahydro-derivative (II) by a soil isolated fungal strain Rhizopus oryzae. In fact, R. oryzae is more versatile in its ability to transform lavandulol compared to the fungus tested earlier (Nankai et al., 1997, Nankai et al., 1998). Five metabolites for I and two metabolites for II from fermentation medium were isolated and characterized.

Section snippets

Chemicals and reagents

Lavandulol was purchased from Sigma–Aldrich. Media ingredients, salts and acids were purchased from HiMedia Laboratories, Mumbai, India. Tetrahydrolavandulol was purchased from ABCR GmbH & Co KG, Germany.

Microorganism

The microorganism used in the present study was isolated from soil collected underneath eucalyptus tree. The organism was maintained and propagated on potato dextrose agar slants. The fungal strain used in the study was identified by sequencing ITS1 and ITS2 region, it showed best match with R.

Results and discussion

To investigate the biotransformation of I and II, 30 fungal systems were screened. The GC and GC–MS analyses of the crude extract after incubating three days of I and II revealed that the soil isolated fungal strain R. oryzae efficiently transformed both I and II into corresponding oxygenated metabolites. All other fungal systems did not produce noticeable transformation for the isolation and characterization of metabolites. Hence, R. oryzae was selected for biotransformation study of I and II.

Conclusion

The soil isolated fungal system R. oryzae has a potential to hydroxylate at allylic positions or at tertiary positions or carryout epoxidation of the double bonds on acyclic monoterpenoids, lavandulol (I) and tetrahydrolavandulol (II) in a highly efficient manner to produce various hydroxylated derivatives of I and II which might be useful in pheromone components, perfumes and cosmetics.

Acknowledgements

P.D. thanks CSIR-New Delhi for fellowship. H.V.T. is grateful for the encouragement of Dr. S. Sivaram, Dr. B.D. Kulkarni, and Dr. Girish Sahni. This work was supported by CSIR Network grant and the Director, NCL, Pune.

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