Free radical scavenging and antiproliferative evaluation of the Olax viridis Oliv. (Olacaceae) whole root

Olax viridis Oliv (Olacaceae) has numerous ethnomedicinal uses including treatment of breast cancer. The study aimed at evaluating the free radical scavenging and antiproliferative activities of O. viridis whole root and the phytoconstituents responsible for this activity. The sample was defatted using n-hexane(NHE), further extracted by cold maceration using absolute methanol to obtain crude extract which was subjected to liquid-liquid partitioning using dichloromethane to afford the dichloromethane fraction (DCM) and aqueous methanol fraction (MEF). Further precipitation of some aqueous methanol fraction (MEF) using acetone yielded saponin-rich fraction (SRF). Furthermore, acid hydrolysis of the SRF gave the sapogenin-rich fraction (ASRF). These extract/fractions: NHE, DCM.,MEF, SRF and ASRF were used for further investigation. Phytochemical screening of fractions was carried out using standard phytochemical methods. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay was used for antioxidant evaluation in vitro with ascorbic acid as the reference standard for comparison while antiproliferative (AP) activity was by cell viability using yeast (Saccharomyces cerevisae) as a model organism. O. viridis whole root contains carbohydrate, cardiac glycoside, steroids, triterpenes and saponins. The fractions showed dose-dependent activities for DPPH radical scavenging activity with the trend at 1 mg/ml thus: DCM (77.53%) >ASRF(70.60%) >SRF(46.82%) >MEF(33.50%) >NHE(22.83%) and the promising fractions showed median concentration; ASRF(IC₅₀=0.54 mg/ml) >DCM(IC₅₀=0.55 mg/ml). All the fractions showed dose dependent antiproliferative activities ASRF(IC₅₀=3.35 mg/ml) >SRF(IC₅₀=5.10 mg/ml) >MEF(IC₅₀=6.28 mg/ml) >DCM(IC₅₀=7.44 mg/ml). Sapogenin may be responsible for the AP and antioxidant activities as ASRF which contains triterpenidal/steroidal nucleus showed a promising activity compared to other fractions. This study validated the traditional use of Olax species in the treatment of cancer.