Antimicrobial, antioxidant activities and chemical composition of selected Thai spices

Abstract

Nine volatile oils and six methanol extracts from Ocimum americanum, O. basilicum, O. sanctum, Citrus hystrix, Alpinia galanga, Curcuma zedoaria, Kaempferia parviflora and Zingiber cassumunar were assessed for antimicrobial and antioxidant activities. The volatile oils and extracts were investigated against eight bacteria and three fungi. The results illustrated that O. americanum volatile oil exhibited broad spectrum activity against tested bacteria with the MICs ranging 1.4-3.6 mg/ml and Candida spp. with the MICs ranging from 0.5-0.6 mg/ml. The O. sanctum volatile oil showed a considerable activity against only Candida spp. with the MICs ranging from 0.8-1.4 mg/ml. Interestingly, growth of Mycobacterium phlei was inhibited by the volatiles of O. americanum, C. hystrix peel, and C. zedoaria with MIC of 1.7, 3.5 and 1.2 mg/ml, respectively. For antioxidant activity evaluation, the methanol extracts of C. hystrix (leaf and peel) and K. parviflora had potent antioxidant activity by the radical-scavenging DPPH method with IC50 of 24.6, 66.3 and 61.5 mg/ml, respectively. GC-MS analysis revealed the typical chemical profiles of the volatile oils. The major component showed the characteristics of the volatile oils and was probably responsible for the antimicrobial effect.