Pharmacognostic study of two medicinal species of Rytigynia (Rubiaceae): Rytigynia nigerica (S. Moore) Robyns and Rytigynia umbellulata (Hierns) Robyns from Nigeria

Micromorphological and phytochemical studies were carried out on the leaves of Rytigynia nigerica (S. Moore) Robyns and Rytigynia umbellulata (Hierns) Robyns. The epidermal cells of both the adaxial and the abaxial surfaces have irregular shape and the anticlinal cell wall patterns are either curved or undulate. Remarkable diagnostic features of the two plants which in a way justify their grouping in the same genus are paracytic stomatal type, hypostomatic leaf and centrally located vascular bundles in the midrib and spatial deposition of crystals of calcium oxalate in the perivascular tissue. But the distinctive features of each species include higher epidermal cell number in R. nigerica than R. umbellulata. Thin cell wall of 1.0 (1.6±0.2) 3.0µm on the abaxial surface of R. nigerica. Higher stomatal size of 6.0 (12.4±1.2) 20µm x 5.0 (13.4±1.3) 20µm in R. umbellulata and long and tip bent trichomes reported on the abaxial surface of R. nigerica and multicellular glandular type on the adaxial layer of R. umbellulata. Phytochemical screening showed that in both R. nigerica and R. umbellulata, bioactive compounds such as alkaloids, tannins, saponins, reducing sugar, glycosides, flavonoids and terpenes were present; whereas anthraquinones, cardiac glycosides, cyanogenetic glycosides and phlobatannins were absent. However, only the extracts of R. nigerica were positive for steroids. These bioactive compounds found in the leaves of these plants play a major role in their medicinal potentials. The two species are well known plants used in folkloric medicine in Nigeria.