Potential antiinfective agents from Eriodictyon angustifolium Nutt. and Salvia apiana Jeps.

The dichloromethane extracts of twelve US Southwestern herbal remedies were tested against Staphylococcus aureus (9-29 UA), Bacillus subtilis (2-27 UA), Klebsiella pneumoniae (3-9 UA), and Candida brassicae (IFO 1664) in an agar dilution-streak bioassay at 1000 μg/ml. All twelve plants inhibited the growth of B. subtilis. Anemopsis californica, Berberis fendleri, Cacalia decomposita, and Eriodictyon angustifolium inhibited the growth of at least two organisms. Salvia apiana was the only plant in this study to completely inhibit the growth of all four test organisms. After a literature search led to the elimination of A. californica, B. fendleri, and C. decomposita from further study due to reports of their bioactive compounds, Eriodictyon angustifolium Nutt. and Salvia apiana Jeps. were subjected to a detailed bioassay directed chemical investigation. Compounds were isolated by solvent extraction, fractionation and standard chromatographic techniques. They were identified by infrared, mass, and nuclear magnetic resonance spectral analyses, comparison with published spectra and comparison with authentic samples when available. Benzyl-trans-4-coumarate was isolated from E. angustifolium following high performance reverse phase liquid chromatography and subsequently synthesized through the condensation of p-coumaric acid and benzyl alcohol. Estimated at 2.9% of the dichloromethane extract, benzylcoumarate was active against S. aureus (100 μg/ml), B. subtilis (50 μg/ml), and C. albicans (25 μg/ml). Also isolated from E. angustifolium were five flavanones: 4',5,7-trihydroxy-flavanone (naringenin), 4',5-dihydroxy-7-methoxy-flavanone (sakuranetin), 3'-methoxy-4', 5',7-trihydroxy-flavanone (homoeriodictyol), 4',5-dihydroxy-3',7-dimethoxy-flavanone, and 5,7-dihydroxy-3',4'-dimethoxy-flavanone. The dichloromethane extract of S. apiana gave an acid fraction from which the abietane diterpenes carnosic acid and its 16-hydroxy derivative were isolated as their methyl ester acetates. Unstable as free carboxylic acids, these compounds retained activity after methylation but lost activity upon acetylation. Methylation without prior acetylation lead to the formation of 11-methoxy-methylcarnosate, 12-methoxy-methylcarnosate, 16-hydroxy-methylcarnosate, 16-hydroxy-11-methoxy-methylcarnosate, 16-hydroxy-12-methoxy-methylcarnosate, and 11,12-dimethoxy-16-hydroxy-methylcarnosate. At 500 μg/ml 12-methoxy-methylcarnosate was inactive while 16-hydroxy-12-methoxy-methylcarnosate was active against S. aureus, B. subtilis, and C. albicans at 250 μg/ml. From this result it was inferred that the introduction of a 16-hydroxy group increased the bioactivity of carnosic acid