Antimycobacterial activity of plant extracts and isolated compounds from plants of the Greek island of Crete

Abstract

Tuberculosis (TB), belongs to the group of neglected diseases. Presently TB is regarded as one of the most dangerous infective diseases worldwide and one of the major AIDS-associated infections thus there is an urgent need to identify new anti-TB agents. In a continuation of our studies to identify plant extracts and bioactive compounds with antiparasitic activity [1] derived from biodiversity hotspots we have studied plants from the Greek island of Crete. Different parts of sixty five plant species were collected and extracted producing more than 250 extracts. Their antimycobacterial activity was evaluated against replicating and non-replicating cultures using MABA [2,3] and LORA [4] methods, respectively. Among the most active plant extracts were those of Astragalus, Atractylis, Echinops, Inula, Eryngium and Cistus species. The later was further investigated and fractions and pure compounds were also evaluated for their activity. More specifically eleven cis-clerodane diterpenes, seven labdane type diterpenes and one triterpene isolated from Cistus monspeliensis and the resin „Ladano“ of Cistus creticus subsp. creticus were evaluated against M. tuberculosis. MIC90 values were calculated for the most active compounds. Most active, found to be a labdane with an MIC90 value of 22.6µg/ml in the LORA assay.