Leaf essential oil of Piper barbatum H.B.K. (Piperaceae) from Peru

Journal of Essential Oil Research: JEOR, May/Jun 2003 by Vargas, Liliana, Perez-Alonso, Maria Jose, Velasco-Negueruela, Arturo, Pala-Paul, Jesus, Vallejo, Maria Concepcion Garcia

Abstract

A steam distilled oil obtained from the leaves of Piper barbatum H.B.K., grown in Peru, in the Amazon basin, was analyzed by capillary GC and GC/MS. Fifty-three components amounting to 98.3% of the oil were characterized from which 17 (totalling 86.6%) were found to be arylpropanoids. The oil contained 2-methoxy-4,5-- methylenedioxypropiophenone (29.5%), alpha-asarone (14.1%), apiole (8.9%), beta-asarone (9.4%), methoxy-4,5-- methylenedioxypropiophenone isomer (10.9%), and (Z)-isoelemicin (9.5%) as major constituents of the oil.

Key Word Index

Piperbarbatum, Piperaceae, essential oil composition, 2-methoxy-4,5-methylenedioxypropiophenone, alpha-asarone, methoxy-4,5-methylenedioxypropiophenone isomer.

Introduction

Piper barbatum in H.B.K. belongs to the Piperaceae family and inhabits in Northern South America, in the Peruvian Amazon basin. As far as we know the oil composition of P. barbatum has not been investigated before. The leaves of this plant known as "Matico hembra, muc-muc" have been used in traditional medicine in the treatment of diarrhoea, intestinal complains, uterine hemorrhages and as an antifungal and antimicrobial (1). As a part of our research on aromatic plants from South America (2), in this work we report on the chemical composition of the oil obtained from the leaves of P barbatum an endemic to the Northern region of South America. Experimental

Plant material: The leaves of Piper barbatum were gathered in the Amazonas Department, Peru. Plant material was collected and identified by Jose Campos. A voucher specimen no. USM-123155 was deposited at the Herbarium of Museo de Historia Natural of San Marcos University, Lima, Peru.

Isolation of volatile constituents: The air-dried plant material was hydrodistilled in an all glass apparatus according to the method recommended in the Spanish Pharmacopoeia, 1997. The oil was dried over anhydrous sodium sulphate and stored at 4 deg C in the dark. The yield was 0.4% based on dried weight of sample.

Analyses: Analytical GC was carried out on a Varian 3300 gas chromatograph fitted with a Silicone MFE1 capillary column (50 in x 0.25 mm, film thickness 0.25 (mu)m); carrier gas N^sub 2^, flow rate 1.5 mL/min, split mode, temperature programmed from 95 deg-240 deg C at 4 deg C/min. Injector temperature 250 deg C, detector used FID, detector temperature 300 deg C. Injection volume for all samples was 0.1 (mu)L.

GC/MS analyses were carried out on a Hewlett Packard 5890 gas chromatograph fitted with two capillary columns of different stationary phases: 1. a phase bonded poly (5% diphenyl, 95% dimethylsiloxane) silicone PTE-5 capillary column (30 in x 0.25 min, film thickness 0.25 (mu)m); and 2. a Supelcowax-10 capillary column (50 in x 0.25 mm, film thickness 0.25 pin). Carrier gas He, flow rate 1.5 mL/min. Temperature program regimen was 70 deg C (2 min) and then programmed to 250"C at 2 deg C/min. Injector temperature 250 deg C. The chromatograph was coupled to a HP 5971 A mass selective detector (70 eV). Many constituents were identified by comparing their retention indices with those of authentic standards available in the author's laboratory. The latter were purchased, synthesized or identified in oils of other species, particularly Apiaceae of known arylpropanoid components. The fragmentation patterns of mass spectra were compared with those stored in the spectrometer database using the NBS54K.L and WILEY. L built-in libraries and with those reported in the literature (3-6).

Results and Discussion

The components of the oil and the percentage of each constituent are summarized in Table I. The components are arranged in their elution order on the silicone column. The oil was characterized by a high content of arylpropanoids, 2-- methoxy-4,5-methylenedioxypropiophenone (29.5%), alpha-- asarone (14.1%), apiole (8.9%), beta-asarone (9.4%), methoxy-4,5-methylenedioxypropiophenone isomer (10.9%),

and (Z)-isoelemicin (9.5%) were the major ones. It is worth mentioning the high percentages. It in this oil of arylpropiophenones (40.7%). The major component, 2-- methoxy-4,5-methylenedioxypropiophenone has also been found in P. marginatum Jacq., together with 3,4-- methylenedioxypropiophenone and 2-hydroxy-4,5-- methylenedioxypropiophenone (7). Outside the Piperaceae, propiophenones have been found in Aristolochiaceae (7), Apiaceae (8,9), latifolone or crocatone, 3-methoxy-4,5-- methylenedioxypropiophenone. As methylenedioxyphenyl substituents and other arypropanoids have been reported (9,10) to have antimicrobial activities, the high content of these compounds in the leaves of P. barbatm may best explain the medicinal properties of this plant.

References

1 L. Vargas, Investigacion de especies vegetales Peruanas con actividad

antifungica. Ph. D. Thesis, Facultad de Farmacia, Universidad de Barcelona (1998).

2. A. Velasco-Negueruela, M. J. Perez-Alonso, C. A. Guzman, J. A. Zygadlo, L. A. Espinar, J. Sanz and M. C. Garcia Vallejo, Volatile constituents of four Lippia species from Cordoba, Argentina. J. Essent. Oil Res., 5, 513-524 1993)