Abstract
Psychotria nilgiriensis was used in traditional medicine as to cure chronic
inflammatory diseases. Therefore, the evaluation of different combination of solventbased fractions from stem and leaves of P. nilgiriensis for free radical scavenging
activity, inhibitory potential against nitric oxide radicals, and tentative identification of
active metabolites were carried out. The antioxidant activity of solvent extracts was
determined by DPPH·
scavenging, TAC, and ORAC assays using spectrophotometer
analysis. Further, nitric oxide production inhibition was studied in lipopolysaccharide
(LPS)-activated macrophages RAW 264.7 cells. Fraction-based bioactive chemical
compound identification was performed using an LC-MS metabolomics approach.
With each of the assays, activity was observed with various extracts derived from both
the stem and the leaf. The two active extracts, one obtained with Psychotria nilgiriensis
leaf ethyl acetate: methanol (PLEM, 40/60 v/v), and another one obtained with P.
nilgiriensis stem chloroform: ethyl acetate (PSCE, 70/30 v/v), about 10-15% of the
chemical components were identified. With PLEM, N,N-bis(2-ethylhexyl)hydroxylamine was higher in concentration, whereas PSCE, N,N-dioctylhydroxylamine was
higher in concentration compared to other metabolites. Thus, the present findings
suggest that the P. nilgiriensis leaf and stem could have medicinal value as an
antioxidant for the treatment of inflammatory diseases. Some of the chemical
constituents such as hydroxylamine derivatives could also be of value.