Assessing essential oil components as plant-based preservatives against fungi that deteriorate herbal raw materials

This study assesses the antifungal efficacy of 14 essential oil (EO) components and some of their combinations as inhibitory to the growth of the aflatoxigenic fungus Aspergillus flavus LHPA(9) isolated from biodeteriorating Asparagus racemosus herbal raw materials. The aim was to determine whether they could be recommended as plant-based preservatives for enhancement of the shelf life of herbal raw materials. Thymol, eugenol, menthol, and their combinations were highly efficacious as their minimum inhibitory concentration (MIC) for inhibition of fungal growth as well as aflatoxin B-1 secretion was less than 1.0 mu l ml(-1). Geranyl acetate, linalool, beta-asarone, 1, 8-cineol, and E-citral were moderately antifungal as their MIC ranged between 1.0 and 5.0 mu l ml(-1). During antioxidant activity 2, 2-diphenyl-1-picrylhydrazyl assay, thymol, eugenol, and beta-caryophyllene showed strong radical scavenging activity, whereas beta-asarone and p-cymene showed moderate activity. Some combinations of EO components showed synergism while others exhibited an additive or antagonism effect in their activity. The findings point to a recommendation that EO components are good alternatives to synthetic preservatives to prevent deterioration of stored herbal raw materials by fungal and aflatoxin contamination and free-radical oxidation. (C) 2013 Elsevier Ltd. All rights reserved.