Screening of Six Medicinal Plant Extracts Obtained by Two Conventional Methods and Supercritical CO₂ Extraction Targeted on Coumarin Content, 2,2-Diphenyl-1-picrylhydrazyl Radical Scavenging Capacity and Total Phenols Content.

Maja Molnar,Drago Šubarić,Blanka Bilić Rajs,Stela Jokić,Krunoslav Aladić,Igor Jerković,Dragica Suknović

doi:10.3390/molecules22030348

Abstract

Six medicinal plants Helichrysum italicum (Roth) G. Don, Angelica archangelica L., Lavandula officinalis L., Salvia officinalis L., Melilotus officinalis L., and Ruta graveolens L. were used. The aim of the study was to compare their extracts obtained by Soxhlet (hexane) extraction, maceration with ethanol (EtOH), and supercritical CO2 extraction (SC-CO2) targeted on coumarin content (by high performance liquid chromatography with ultraviolet detection, HPLC-UV), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging capacity, and total phenols (TPs) content (by Folin–Ciocalteu assay). The highest extraction yields were obtained by EtOH, followed by hexane and SC-CO2. The highest coumarin content (316.37 mg/100 g) was found in M. officinalis EtOH extracts, but its SC-CO2 extraction yield was very low for further investigation. Coumarin was also found in SC-CO2 extracts of S. officinalis, R. graveolens, A. archangelica, and L. officinalis. EtOH extracts of all plants exhibited the highest DPPH scavenging capacity. SC-CO2 extracts exhibited antiradical capacity similar to hexane extracts, while S. officinalis SC-CO2 extracts were the most potent (95.7%). EtOH extracts contained the most TPs (up to 132.1 mg gallic acid equivalents (GAE)/g from H. italicum) in comparison to hexane or SC-CO2 extracts. TPs content was highly correlated to the DPPH scavenging capacity of the extracts. The results indicate that for comprehensive screening of different medicinal plants, various extraction techniques should be used in order to get a better insight into their components content or antiradical capacity.

Highlights

Medicinal plants are rich in bioactive compounds with protective and healing properties that are often present in low concentrations
The research was designed to compare the extracts obtained by SC-SO2 with hexane extracts, and to compare the extracts obtained by SC-SO2 with EtOH extracts with respect to the extraction yields, coumarin content, diphenyl-1-picrylhydrazyl radical (DPPH) scavenging capacity, and total phenols (TPs) content of the obtained extracts
This study provides insight into different extraction techniques and conditions for the preparation of medicinal plant extracts considering extraction yield, coumarin content and antiradical capacity

Summary

Introduction

Medicinal plants are rich in bioactive compounds with protective and healing properties that are often present in low concentrations Since they are often chemically sensitive, it is very important to select an appropriate method for their isolation, purification, and quantification. Coumarins are widely distributed in various plant families, such as Apiaceae, Asteraceae, Fabiaceae, Rosaceae, Rubiaceae, Solanaceae, especially Rutaceae and Umbelliferae [1,2,3,4]. They can be distributed in all plant parts depending on the growing conditions [3]; they act as phytoalexins, and are biosynthesized when the plant is subjected to adverse conditions like wilting, disease, or drought. Various extraction techniques have been employed for the isolation of coumarins from various plant materials, such as maceration, ultrasound maceration, or infusion with aqueous ethanol, water, methanol, ethyl acetate, chloroform, diethyl ether, or other solvents [17,18,19,20]

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