Ocimum species (Ocimum tenuiflorum, Ocimum gratissimum & Croton bonplandianus) and Mentha spicata are having various medicinal properties. The substances derived from the plants remain on the basis for a large proportion of the commercial medications used today for the treatment of diseases. Therefore, one of the main objectives of the study was to analyze the phytochemical content, genetic similarity and distance between these three species of ocimum and one of mentha. All the prepared plant extracts were subjected to preliminary phytochemical screening for the presence of glycosides, saponins, alkaloids, flavonoids, tannins, proteins, free amino acids, carbohydrate and vitamin C. Another objective of the study is to provide a simple method of isolation of DNA, using the CTAB extraction protocol by phenol chloroform method. DNA quantity obtained was comparable to the known standard DNA concentration curve at 600nm. Good quality of DNA was isolated and suitable for various molecular biology applications.