Isolation and Antioxidant Activity of Harmalol from Grewia villosa Willd. Stem and Root Bark

Julia Kimondo; Peggoty Mutai; Peter Njogu; Charles Kimwele; Purity Ochieng; Abiy Yenesew

Julia Kimondo Department of Pharmacology & Pharmacognosy, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000 – 00200, Nairobi, Kenya
Peggoty Mutai Department of Pharmaceutical Chemistry, Pharmaceutics & Pharmacognosy, University of Nairobi, P.O. Box 19676-00202, Nairobi, Kenya
Peter Njogu Department of Pharmaceutical Chemistry, Pharmaceutics & Pharmacognosy, University of Nairobi, P.O. Box 19676-00202, Nairobi, Kenya
Charles Kimwele Department of Veterinary Anatomy & Physiology, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya
Purity Ochieng Department of Chemistry, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya
Abiy Yenesew Department of Chemistry, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya

Keywords: Grewia villosa, isolation, harmalol, antioxidant

Abstract

Grewia villosa Willd. is a deciduous shrub found in arid parts of Kenya and used as both food and medicine. The study aimed to isolate compounds present in Grewia villosa stem and root bark extract and assess their antioxidant activity. Grewia villosa stem and root bark were collected from Loitokitok, Kajiado County, Kenya. They were dried in the shade, pulverized to fine powder, and extracted in methanol/dichloromethane 1:1 mixture for 72 h. The solvent was removed by rotary evaporation. The crude extract was subjected to column chromatography over silica gel to obtain one pure compound. Analysis by mass spectrometry and nuclear magnetic resonance spectroscopy identified the isolated pure compound as 1-methyl-4,9-dihydro-3H-β-carbolin-7-ol (harmalol). Antioxidant activity was performed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) standard protocol. Harmalol displayed significant antioxidant activity (115.22 µg/ml) comparable to that of the methanol extract. This compound was previously isolated from the root of G. villosa but was not fully characterized spectroscopically. This study is the first report of NMR characterization of harmalol.