The purpose of the study was to assess biological activities of secondary metabolites in selected medicinal plants used for treating inflammation and associated complications and characterization of antimicrobial compounds from the plant extracts of South African Pomaria sandersonii(Fabaceae) and Alepidea amatymbica(Rubiaceae) roots used in Zulu traditional medicine. The specific objectives were to assess free radical scavenging activity of the plant extracts, different fractions obtained by solvent-solvent extraction and isolation of biologically active compounds. Furthermore, antimicrobial and anti- inflammatory activities of the plant crude extracts and different fractions were tested. Biologically active compounds were isolated, characterized and their structures elucidated using NMR and MS. The biological activities reported for Pomaria sandersonii were for the very first time in literature. Three were new novel compounds were isolated during this investigation. These include two diterpenes, 14 acetoxo-12-oxokaur-16-en-19-oic acid; 16-hydroxy-kaur-6-en-19-oic-acid from Alepidea amatymbica and a chalcone dimer isolated for the first time from Pomaria sandersonii.