# Metabolomics, antioxidant, and enzyme inhibitory effects of Citrus aurantium fruits

## TL;DR

This study identifies key compounds in bitter orange fruits and leaves and shows their potential as antioxidants and enzyme inhibitors.

## Contribution

First-time GC-MS analysis of Citrus aurantium hexane extracts and their enzyme inhibitory effects confirmed by in silico docking.

## Key findings

- Fruit extract contains nootkatone, decyl anthranilate, neryl acetate, and linalool acetate as major components.
- Leaf extract is rich in lupeol, linalool, friedelan-3-one, and linalool acetate.
- Extracts show strong enzyme inhibitory activity, with lupeol and linalool acetate showing best binding affinities.

## Abstract

The genus Citrus comprises a large number of economically important fruit crops. They are recognized globally as functional foods and in the food, pharmaceutical, and cosmetic industries.

We present herein the chemical composition of the hexane extracts of Citrus aurantium (bitter orange) fruits and leaves by GC-MS for the first time, in addition to their antioxidant and enzyme inhibitory activities in vitro.

GC-MS revealed nootkatone (15.29%), decyl anthranilate (11.58%), neryl acetate (7.83%), and linalool acetate (6.83%) as major components of fruit extract; while the leaves extract contained mainly lupeol (24.32%), linalool (16.47%), friedelan-3-one (16.40%) and linalool acetate (12.31%). The extracts showed potential inhibitory activities against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, amylase, and glucosidase enzymes. Results were confirmed by in silico molecular docking studies on the respective enzymes' active sites, viz NADPH oxidase, BChE, tyrosinase, α-amylase, and α-glucosidase. Amongst the docked compounds, lupeol showed the best binding affinities to NADPH oxidase, butyrylcholinesterase BChE, and α- glucosidase; while linalool acetate and neryl acetate showed the best activities against tyrosinase and α-amylase enzymes, respectively. In conclusion, bitter orange waste products can be a potentially important source of antioxidants and useful supplements.