DNRL was prepared from the fresh NRL that collected from Hevea brasiliensis (RRIM 600 clone) via
the technique developed by our group [5]. HPMC was obtained from Onimax (China). DBP was obtained
from Sigma-Aldrich (USA.). Oleic acid, IPP, PG, olive oil and menthol were purchased from P.C. Drug
Center (Thailand). All chemicals were pharmaceutical grade and used as received.