The root samples of S. collinsiae were collected from Wang Num
Kheo District, Nakhon Ratchasima Province, Thailand in January
2010. The samples were identified by Dr. Srunya Vajrodaya, Faculty
of Botany, Kasetsart University, Thailand and the voucher specimens
were deposited at Department of Pharmacognosy, Faculty
of Pharmacy, Mahidol University, Bangkok, Thailand. Each sample
was washed thoroughly with tap water, cut into small pieces and
dried in a hot air oven at 50 ◦C for 72 h. The dried sample was ground
into powder, passed through a sieve (60 mesh) and stored in an
air-tight container until used