Abstract:
There are four Strychnos species in Thailand including Strychnos thorelii, S. lucida, S. nux-vomica and S. nux-blanda which presented as important medicinal plants in folk medicine. Strychnos species have several ethnobotanical usage, they play an important role against fever, pain, antidote for snake poisoning and rheumatism. Many Strychnos species possess the similar morphology and vernacular name resulting in unintentional substitution. This current research aimed to investigate leaf microscopic characteristics and leaf measurement (stomatal number, stomatal index, palisade ratio, veinlet termination number, epidermal cell number and epidermal cell area) among four Strychnos species. The results showed paracytic type of stomata. There are no trichomes or cicatrices on both adaxial and abaxial epidermis. The leaf constants among four species are able to differentiate the Strychnos species, especially stomatal index which is highest in S. nux-blanda (range 15.24-16.44) and lowest in S. lucida (range 6.77-7.52). The full-length of nucleotide sequencing ITS region, rbcL and matK gene were also evaluated and the result showed the sequence length in ITS region, rbcL and matK gene were approximately 700, 1400 and 1800 base pairs respectively. The intra-species of three sequence shown 95-99% similarity and the inter-species of three sequence shown 87-99% similarity. PCR-RFLP method based on the matK gene was developed. After digestion with specific restriction enzyme using DraI and XbaI, four Strychnos species were easily distinguished based on the different sizes of the digested fragments. In conclusion, the use of both microscopic and molecular analyses are successful for the identification of Strychnos species in Thailand.
