**Antiradical and Xanthine Oxidase Inhibitory Activity Evaluations of** *Averrhoa bilimbi* **L. Leaves and Tentative Identification of Bioactive Constituents through LC-QTOF-MS/MS and Molecular Docking Approach**

#### **Qamar Uddin Ahmed 1,\*, Alhassan Muhammad Alhassan 1,2,\*, Alfi Khatib 1, Syed Adnan Ali Shah 3,4, Muhammad Mahmudul Hasan 1 and Murni Nazira Sarian 1**


Received: 3 July 2018; Accepted: 25 September 2018; Published: 8 October 2018

**Abstract:** The objective of the present study was to investigate the antiradical and xanthine oxidase inhibitory effects of *Averrhoa bilimbi* leaves. Hence, crude methanolic leaves extract and its resultant fractions, namely hexane, chloroform, and n-butanol were evaluated for 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging effect and xanthine oxidase inhibitory activity. The active constituents were tentatively identified through LC-QTOF-MS/MS and molecular docking approaches. The n-butanol fraction of *A. bilimbi* crude methanolic leaves extract displayed significant DPPH radical scavenging effect with IC50 (4.14 ± 0.21 μg/mL) (*p* < 0.05), as well as xanthine oxidase inhibitory activity with IC50 (64.84 ± 3.93 μg/mL) (*p* < 0.05). Afzelechin 3-*O*-alpha-L-rhamnopyranoside and cucumerin A were tentatively identified as possible metabolites that contribute to the antioxidant activity of the n-butanol fraction.

**Keywords:** *Averrhoa bilimbi*; Oxalidaceae; DPPH; xanthine oxidase; LC-QTOF-MS/MS; molecular docking; tentative bioactive constituents
