Author(s): Abo-Khatwa, A.N., Al-Robai, A.A. and Al-Jawhari, D.A.
Article publication date: 1997-04-01
Vol. 15 No. 1 (yearly), pp. 15-28.
200
Keywords
Usnic acid, Saudi Arabia, Atranorin
Abstract
(+) Usnic acid (2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-1.3(2H, 9bH)-dibenzofuran Dione), an antibiotic, was found in large amount (about I % based on dry weight) in the Saudi-Arabia lichen Usnea articulata which grows in abundance on the Asir mountains of the South-Western region. This finding was confirmed by various chemical means including mass spectra, NMR, IR, UV spectrometry and polarimetry. Atranorin (3-formyl-2,4-dihYdroxy-6-methylbenzoic acid 3-hydroxy-4-(methoxycarbonyl)-2,5-dimethylphenyl ester), of a less known medical importance, was found in a lesser quantity (about 0.1 %) in the edible lichen Parmelia tinctorum which is consumed as a food spice in some Arab countries (called in Arabic- AI-Sheba). The presence of atranorin, which is known to be a food deterrent for insects and other herbivores, was also confirmed by the preceding methods of chemical analysis.