ABSTRACT

Six medicinally important Senna species were studied in order to provide complementary data from foliar epidermal features, phytochemical contents, antimicrobial properties and DNA fingerprint to aid easy recognition of the Senna species for pharmacognostic researches. This study was carried out in order to eliminate adulteration of these medicinally important Senna species by misidentification. The species studied were S. alata, S. obtusifolia, S. siatnea, S. hirsuta, S. occidentalis and S. polyphylla. The result of foliar epidermal investigation revealed the variation in the epidermal morphology of the six Senna species investigated. The epidermal cell shape varied from polygonal and irregular to sinuous on the lower and upper epidermis ofthe six Senna species investigated. Lower epidermal cells of S. alata, S. occidentals, S. obtusifolia and S. siamea, epidermal cell shape were mostly polygonal, while that of S. hirsuta and S. polyphylla were irregular in shape. The lowest stomatai frequency of 11.5 % and 29.6 % were seen on the upper and lower epidermis of S. siamea and S. obtusifolia respectively. The highest stomatai frequency of 19.8% and 58.3% were observed on upper and lower epidermis of S. obtusifolia and S. alata respectively. Trichomes were seen in all species. The uniformity in most ofthe epidermal features shows the close affinities that exist among these species and the naturalness of the Senna species in general. S. alata contained the highest alkaloid content (1.16 mg/1), followed by S. hirsuta (1.03 mg/1) and the least was in Senna occidentalis (0.17 mg/1). This was the same trend of S. alata having higher phytochemical constituents except for phytates were the highest was recorded for S. siamea (0.36 mg/1). The study on antimicrobial activities show that ethanolic extracts of the six Senna species possess antimicrobial activity against human pathogens used in this study, Escherichia coli, Klebssiella pneumonia, Staphylococcus aureus, Streptococcus pneumonia and Salmonella typhi. The antimicrobial activity of S. alata was more pronounced at higher concentration than at lower concentration in the species of Senna investigated. This is in conformity to the phytochemical content.where S. alata had the highest phytochemical content. The antimicrobial activity of ethanolic extract ofSenna alata was favourably compared with the standard drug, ciprofloxacin. From the RAPD analysis, a dendogram generated from the detection of polymorphic fragments in the six primer sequences showed that all the species are at least 62% similar. S. alata and S hirsuta were 95% genetically identical and far fromother accessions in terms of similarity. This is common in speciation. The RAPD analysis led to a clear distinction between S. alata and S. hirsuta and other species. The result ofthe phytochemical and antimicrobial studies have revealed the potency ofthe six Senna species aS active antimicrobial agents, while the result ofthe epidermal and molecular studies aid easy recognition of these medicinally important Senna species for pharmacognostic researches.