The cytotoxic effects, anti-iflammatory, antioxidant, antibacterial, and antidiabetic properties of eight selected South African plants for medicinal purposes.

Doctoral Degree. University of KwaZulu-Natal, Durban.People from the Southern African region have been using the fauna and flora of the region in their homes for millennia to treat all sorts of ailments and complaints with great success. This knowledge transfer was done through ’apprenticeships’ and oral communication. Certain communities consider medicinal plants to be safer than drugs and that they can treat more than one ailment. This study investigated cytotoxic effect, antimicrobial, anti-inflammatory, antioxidant, and antidiabetic properties of eight selected South African plants for medicinal purposes. Plant species were collected from the Walter Sisulu National Botanical-Gardens and were extracted with 90% methanol (1 g/10 ml) and concentrate to 10 mg/ml. Antimicrobial activities were determined by the microplate dilution method to establish the ability of the plant extracts to inhibit or kill pathogenic organisms with minimal inhibitory concentrations and minimum bactericidal concentration. Cytotoxicity effects were determined with Alamar blue and crystal violet cell viability assays, against C2C12 and RAW 264.7 cells. Anti-inflammatory effects were identified with stimulated lipopolysaccharide RAW 264.7 cells, and nitric oxide inhibition was measured with Griess reagent assay. The estimation of preliminary phytochemical, antioxidant (DPPH and ABTS radical scavenging), and alpha-amylase inhibition were determined with standard methods. The plant extracts inhibition and bactericidal effects were observed against all bacteria, namely: Lippia javanica (0.25±0.00 to 1.13±0.29 mg/ml); Ziziphus mucronata leaf (0.44±0.00 to 1.00±0.00 mg/ml); Erythrina lysistemon (0.44±0.00 to 1.08±0.00 mg/ml) and Schkuhria pinnata (0.5±0.00 to 1.34±0.00 mg/ml). All plant extracts exhibited flavonoids, phenols, terpenoids, and coumarins. The antioxidant inhibition was observed above 80% for Schkuhria pinnata, Lippia javanica, Clerodendrum myricoides, and Erythrina lysistemon. Also, these plant species exhibited an alpha-amylase inhibitory effect of 80%. The IC50 values were > 1000 μg/ml. All plant extracts demonstrated some degree of an antiinflammatory effect. However, Clerondendrum myricoides (35% - 89%), Lippia javanica (26% - 77%), Erythrina lysistemon (23% - 76%), Schkuhria pinnata (27% - 65%), and Vernonia oligocephala (16% - 58%) with IC50 value >1000 μg/ml, exhibited a marked antiinflammatory effect. Therefore, the presence of phenolic, flavonoids, anti-inflammatory, antioxidants, and α-amylase properties are potential solutions towards the management of diabetes and other chronic inflammatory diseases. Keywords: medicinal plants, antimicrobial, cytotoxicity, anti-inflammatory, antidiabetic, antioxidant