The present invention relates to a selectively purified tanshinone compounds containing extract from the root of a Salvia spp comprising Cryptotanshinone, Dihydrotanshinone, Tanshinone I, and Tanshinone IIA. It comprises at least 15%, by weight of the said identified tanshinone compounds and at least 4% by weight, of cryptotanshinone. The extract and formulations thereof have been found to exhibit excellent anti-microbial properties against, in particular MRSA.
