Two new bisabolene diols from the stem wood essential oil of Vanillosmopsis erythropappa Schultz-Bip. (asteraceae)

Journal of Essential Oil Research: JEOR, May/Jun 2003 by Braun, Norbert A, Meier, Manfred, Kohlenberg, Birgit, Hammerschmidt, Franz-Josef

Abstract

The stein wood oil of Vanilosmopsis enjthropappa Schultz-Bip. was analyzed using GC/MS. Forty-three constituents were identified: 31 sesquiterpenoids, one phenylpropane and 11 others. 2-Bisabolene-7,11-dial and 10bisabolene-3,7-dial were found for the first time in nature and were characterized using 'H-, IIC-NMR, GC/FTIR and GC/MS analyses.

Key Word Index

Vanillosmopsis erjthropappa Schultz-Bip., Asteraceae, essential oil composition, 2-bisabolene-7,11-diol, 10-- bisabolene-3,7-diol, (-)-alpha-bisabolol

Introduction

The sesquiterpene alcohol cc-bisabolol [= 2,10-- bisaboladien-7-ol (1) 1 has four possible stereoisomers and all four have been isolated from the essential oils of a variety of plants, shrubs and trees (2,3). Chamomile-derived (-)-(6S,7S)-- oc-bisabolol is frequently used in pharmaceutical and cosmetic products (4) due to its anti-inflammatory mode of action (5,6). Besides Chamomilla recutita (L.) Rauschert (syn.: Matricaria recutita L.; M. chanimitilla L.), there are two other main natural sources of(-)-aalpha-bisabolol: Vanillosmopsis erythropappa Schultz-Bip. and V. arborea Baker (7,8). The Brazilian trees V. enjthropappa and V arborea, like C. recutita, belong to the family Asteraceae. The steam distilled Vanillo.snwpsis wood oils are commercially used to isolate (-)-alpha-bisabolol (9).

The composition of the oil of V ertthropappa as well as V. arborea has been previously described (10-12). In addition to other components, a hydroxylated alpha-bisabolol [= (6S,7S)2,10-bisaboladiene-7,15-diol] was isolated from V arborea (13). Two other alpha-bisabolol-like diols, 2,11-bisaboladiene7,10-diol and 2,9-bisaboladiene-7,11-diol, were found in Ach illea odorata L., also a member of the Asteraceae. (14). The corresponding monounsaturated 2-bisabolene-7,11-diol [1] and 10-bisabolene-3,7-diol [2] (Figure 1), to the best of our knowledge, have never been isolated nor identified from any natural source (15,16). Herein we report the isolation and stereochemical assignment of sesquiterpene diols [1] and [2] from V. erythropappa and present, in addition, a detailed analysis of the stem wood oil.

Experimental

Plant material: Small stem wood pieces of V enyhropappa Schultz-Bip. were purchased from Puritta Oleos Essenciais-- Industria e Comercio Ltda, Torrinha, Sao Paulo (Brazil). The plant material was originally collected in the south of the Brazilian state Minas Gerais.

Oil isolation: Stem wood chips of V erythropappa (500 g) were hydrodistilled for 13 h to yield 3.5 g (0.7%) of a slightly yellow oil.

Oil analysis: Analytical GC was carried out on a Hewlett Packard 5890 Series II gas chromatograph. A DB-NN,ax column (60 m x 0.25 mm, film thickness 0.25 (mu)m), programmed from 50deg-240degC at 4degC/min, was used with N^sub 2^ as carrier gas. GC/MS analyses were performed either on a Hewlett Packard 5970 (DB-Wax, 60deg-240degC at 4degC/inin) or a Hewlett Packard 5973 (HP-5, 60deg--250degC at 4degC/min) mass spectrometer operating at 70 eV ionization energy. In both cases, the column used was a 60 in x 0.25 mm with a film thickness of 0.25 Jm and He as carrier gas. GC/FTIR was measured on a Hewlett Packard 5965B IRD spectrophotometer (DB-Wax, 60 m x 0.32 min, film thickness 0.50 (mu)m; from 60deg-240degC at 4degC/min; carrier gas: He). HPLC separation was performed with a Knauer HPLC-pump 64 on a 250 mm x 20 mm Eurospher 100 Si 5 (mu)m column from Knauer (flow rate: 10 mL/min, detection: lambda = 240 nm). Optical rotations were measured on a Perkin-Elmer Polarimeter 241 with the concentration (c) expressed in g/100 mL. NMR spectra were recorded on a Varian VXR-300 with 300 MHz (^sup 1^H-NMR) or 75.45 MHz (^sup 13^C-NMR) in CDCI^sup 3^ and using TMS as internal standard.

Oil fractionation: Compound [1] was isolated starting with repeated fractional distillation ofwood oil under reduced pressure [a) Claisen distillation, b) residue distilled on a Kugelrohr (200degC, 10 mbar)], followed by column chromatography (silica gel, Et^sub 2^O) to obtain a colorless highly viscous oil (GC purity: 80%). Fractions were combined according to their composition as assessed by GC. Upon standing in a freezer at -20degC the crude oil solidified and recrystallization from n-hexane gave [1] as colorless crystals.

Acknowledgments

We are indebted to Dragoco Perfumes e Aromas Ltda., Sao Paulo (Brazil) who acquired the plant material for us. We also thank our colleagues Claus-Hermann Kappey and Bernd Holscher for providing the synthetic sample of 2-bisabolene-7,11-dials. The authors express their deep gratitude to Wilhelm Pickenhagen for his support and helpful discussion.

References

1. For nomenclature of terpenoids see: J. D. Connolly and R. A. Hill, Dictionary of Terpenoids - Volume 1. Chapman & Hall, London (1991).

2. E. Flaskamp, G. Nonnenmacher and 0. Isaac, Zur Diastereoisomerie naturlicher and synthetischer a-Bisabolole. Z. Naturforsch., 36b, 114118 (1981) and Correction Z. Naturforsch., 36b, 526 (1981).

3. E. J. Brunke and F. J. Hammerschmidt, Inhaltsstoffe des atherischen Ols von Salvia stenophylla - Isolierung von ( )-epi-a-Bisabolol als Naturstoff. Dragoco Rep., 37-43 (1984).