Pharmacognostic analysis and antimalarial evaluation of quercetin in Ilex umbellulata bark using HPTLC, in vitro screening, molecular docking, and network pharmacology

Abstract

Background

The bark of Ilex umbellulata is traditionally used for the treatment of many diseases such as malaria. Despite its traditional relevance, the pharmacognostic parameters and pharmacological properties remained unexplored. In this study, we aim to develop the missing pharmacognostic parameters with modern analytical techniques and carry out multi-step computational studies to study the antimalarial potential of I. umbellulata.

Results

The bark was 2–6 mm thick, composed of different colored layers, and was bitter-sweet in taste. Powdered microscopy revealed the presence of starch granules, calcium oxalate crystals, cork cells, trichomes, and fibers. Physicochemical properties such as ash values (total, acid-insoluble, and water-soluble), extractive values (petroleum ether, chloroform, ethyl acetate, methanol, aqueous, 80% MeOH), moisture content, swelling index, fluorescence, and pH of the bark were determined. FT-IR fingerprint profiling of petroleum ether, chloroform, ethyl acetate, methanol, aqueous, and 80% MeOH extracts revealed characteristic bands at different wavelengths that are indicative of the presence of certain functional groups. HPTLC fingerprint profiling with a mobile phase of hexane: ethyl acetate: formic acid (4.5:5.5:0.5 v/v) revealed 9 characteristic peaks. With a mobile phase of toluene: ethyl acetate: formic acid (5:4:0.2 v/v), the validated TLC densitometric studies revealed the presence of 2.07 mg of quercetin (R_f = 0.477 ± 0.005) in 100 mg of 80% MeOH bark extract of I. umbellulata. JazQSAR web tool previously developed by us predicts the IC₅₀ of quercetin against Plasmodium falciparum as 3.88 ± 0.35 µM, which was not far from the practically observed value for quercetin. Multi-target molecular docking with a validated docking protocol revealed that quercetin could potentially interact with 20 proteins of P. falciparum that are highly expressed during the schizont and trophozoite stages. Network pharmacology studies revealed that quercetin could potentially alleviate malaria mainly by inhibiting pro-inflammatory response through the action of IL-4, IL-10, and IL-13 and by triggering the immune system.

Conclusions

The pharmacognostic parameters of I. umbellulata bark may be used as quality control parameters to aid in identification and authentication and to prevent adulteration. The results obtained from the multi-target molecular docking and network pharmacology studies support the use of I. umbellulata as a traditional herbal remedy against malaria.