Terpenoid composition and antibacterial assay of whole aerial parts and roots of Plectranthus striatus Wight ex Hook. f.

Plectranthus striatus Wight ex Hook. f., a medicinally important plant of the family Lamiaceae grows wild in the central Himalayan region of Uttarakhand, India. In view of the medicinal importance of this genus and the lack of any report on its essential oil composition and antibacterial activity, the present study was conducted. Volatile constituents from the whole aerial parts and roots of P. striatus were isolated by steam distillation process using a copper still connected to spiral glass condensers and analyzed by GC and GC/MS. A total of 45 compounds from the aerial part and 36 compounds from the roots representing 82.0% and 91.5%, respectively of the total essential oil composition were identified. The major constituents found in the essential oil from the whole aerial parts were phytol (32.0%), phytol acetate (8.3%) and octan-3-ol (6.5%). The major constituents from the essential oil of roots were octan-3-ol (47.4%) and 1-octen-3-ol (33.5%). The essential oil samples from the whole aerial and roots were further assessed for their antibacterial activity against ten different pathogens by using disc diffusion method. The essential oil from the aerial part displayed strong inhibition in initial screening against Xanthomonas phaseoli (14.66 & PLUSMN;1.15 mm), Klebsiella pneumoniae (13.33 & PLUSMN;1.15 mm) and Escherichia coli (13.00 & PLUSMN;2.64 mm) with bactericidal effect observed at lowest concentration of 31.25 & mu;L/mL for Klebsiella pneumoniae and Escherichia coli. On the other hand, the essential oil from the roots showed broad spectrum activity in primary screening towards Pasteurella multocida (21.33 & PLUSMN;0.58 mm), Enterococcus faecalis (21.00 & PLUSMN;1.00 mm), Agrobacterium tumefaciens (20.33 & PLUSMN;0.58 mm) and Salmonella enterica (20.33 & PLUSMN;0.58 mm) with bactericidal effect observed at minimum concentration of 31.25 & mu;L/mL for Pasteurella multocida.