Thesis (M.Sc.)--Chulalongkorn University, 2010

There are four species of plant in the Genus Morinda commonly found in Thailand; Morinda citrifolia L., M. elliptica Ridl., M. umbellata L., and M. coreia Ham. M. citrifolia is used in folk medicine of many countries, including Thailand. M. citrifolia or Yor has been notified as a medicinal plant in Primary Health Care for anti-nauseate and anti-emetic. Due to their relatively high degree of morphological variability and inadequate study of Morinda species, an accurate investigation on their identity is essential. The purpose of this study was to examine the microscopic characteristics including of cross section of midrib, leaf measurement, and the molecular analysis by using PCR-RFLP technique on the ITS regions. The results of leaf measurement of four species followed the previous reported of rubiaceous plants which could be categorized the stomatal cells in Paracytic type and the leaf measurement revealed specific comparative data of which display in the term of constant number. Dichotomous key can be generated from cross section of midrib structure for identification of each species. Along with the molecular analysis, three restriction enzymes (MseI, EcoRI and MspI) have shown distinct and polymorphic of banding pattern from digestion on ITS regions. Based on the differentiation among the digestion pattern Morinda species, it could be applied as molecular marker for discrimination or contamination of samples. In conclusion, both microscopic and molecular analyses were able to authenticate 4 Morinda species.