MATERIALS AND METHODS
Chemicals and Plant Extract. Acetylcholine (ACh), L-phenylephrine
(Phe), sodium nitroprusside (SNP), and 17β-estradiol (E2)
were purchased from Sigma Chemical Co. (St. Louis, MO), and all
other chemicals were of analytical grade. Preparations of plant extracts
and isolation of diarylheptanoid from C. comosa rhizomes were
conducted as previously described.13 Rhizomes of C. comosa were
purchased from Kampaengsaen district, Nakhon Pathom province,
Thailand, and subjected to taxonomic identification18 with voucher
herbarium specimen (SCMU No. 300) deposited at the Department
of Plant Science, Faculty of Science, Mahidol University, Bangkok.