Bioassay-guided isolation and identification of antimicrobial and cytotoxic compounds from the leaves of dicranopteris linearis / Nor Azura Mat Desa

Dicranopteris linearis belongs to the family of Gleicheniaceae known locally in Malay as 'Resam'. Preliminary phytochemical investigation of the crude extracts revealed the presence of flavonoids, saponins, steroids, tannins, and terpenoid. The main aim of this study was to find out the bioactive compounds with potential antimicrobial and cytotoxic activities based on the bioassay-guided fractionation and isolation procedures. Methanol and fractionated extracts (hexane, chloroform and methanol) of D. linearis were investigated for their cytotoxic effects against three cell lines, namely HL60, HCTl16 and MCF7 and one normal cell WRL68 using the MTT assay. The methanol extract was found to be most effective against HL60 (ICso 9.20 ug/ml., respectively). The methanol fraction possessed strong activity against HL60
with ICsoof 12.88 ug/ml. and was fractionated by vacuum liquid chromatography into eleven fractions (FI, F2, F3, F4, F5, F6, F7, F8, F9, FlO and FI1). Only F7 showed the active value with ICso 6.21 ug/ml., Purification of the most bioactive fraction, F7
with column chromatography, radial chromatography and preparative thin layer chromatography resulted in the isolation of four compounds (PCI, PC2, PC3 and PC4). Only PCI and PC2 showed the active value of cytotoxic activity against HL60
with IC50 values of 4.59 and 3.87 ug/ml. respectively. The structure of these compounds were elucidated by spectroscopic methods (lD-NMR, 2-D-NMR, UV, IR and MS) and compared with published data. PCI and PC2 were identified as quercitrin and afzelin, respectively. The micro-broth dilution method was used to
determine the antimicrobial activity against S. aureus 25923 (MSSA), S. aureus 33591 (MRSA), B. subtilis 6633, E. coli 35218, P. aeruginosa 27853 and C. albicans 10231. The highest activity was methanol extracts and methanol fraction with the Minimum Inhibitory Concentration (MIC) values 1250 ug/ml, and 625 ug/ml.. All the fractions Fl until F7 showed the weak antimicrobial activity with the MIC >1250 ug/ml., Hence, the separation into single pure compounds was not possible, resulting in a reduced antimicrobial activity. The objectives as outlined were successfully
achieved only for cytotoxic activity