In total 33 plant species were collected from the herbal garden
maintained at the Horticulture College and Research Institute,
Periakulam, Tamil Nadu, India (Table 1). The fresh leaf samples
collected from all these 33 plant species were brought to the laboratory
immediately, washed in running tap water to remove dust
if any, ground in a sterile mortar and pestle by adding 10 ml of
sterile distilled water for every 10 g of leaf tissue (100% concentration)
and finally filtered through two layers of cheesecloth. The
extract was then centrifuged at 10,000 g for 20 min and the supernatant
was transferred to a fresh tube. The extract was then
sterilized using 0.2 mm disposable syringe filters for further use.