Total Triterpenes, Polyphenols, Flavonoids, and Antioxidant Activity of Bioactive Phytochemicals of Centella asiatica by Different Extraction Techniques

Rasangani Sabaragamuwa; Conrad O Perera

doi:10.3390/foods12213972

Total Triterpenes, Polyphenols, Flavonoids, and Antioxidant Activity of Bioactive Phytochemicals of Centella asiatica by Different Extraction Techniques

Foods. 2023 Oct 30;12(21):3972. doi: 10.3390/foods12213972.

Authors

Rasangani Sabaragamuwa^{1

2}, Conrad O Perera¹

Affiliations

¹ Food Science Programme, School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
² Department of Food Science and Microbiology, School of Science, Auckland University of Technology, Auckland 1142, New Zealand.

Abstract

Obtaining phytochemical-rich plant extracts from natural products where the active ingredients are present in comparatively low levels in the tissue matrix is the critical initial step of any chemical analysis or bioactivity testing. The plant C. asiatica is rich in various phytochemicals, the major constituents being triterpenes and flavonoids, as well as other polyphenols, leading to a number of bioactivities. In this study, an attempt was made to achieve several green technology principles, while optimizing the extraction method for the efficient extraction of bioactive compounds from C. asiatica. Soxhlet extraction (SE), ultrasound-assisted extraction (UAE) with low-frequency sonication, microwave-assisted extraction (MAE) using a closed-vessel microwave digestion system, and subcritical water extraction (SWE) in a high-pressure reactor were employed to extract the bioactive compounds. The solvent system, extraction time, and solid-to-solvent ratio were varied to optimize the extraction. UAE gave the best extraction yield, while MAE gave similar results, with a solid-to-liquid ratio of 1:25, a binary solvent system of 9:1 methanol to water (v/v), and a 20 min extraction time for the extraction of triterpenes, including madecassoside, asiaticoside, madicassic acid, and asiatic acid. Investigation of different solvent systems based on water and methanol also revealed information on the extraction behavior of total triterpene content (TTC), total polyphenolic content (TPC), total flavonoid content (TFC), and the variations in the antioxidant capacity of the extracts. In this study, it was evident that UAE and MAE offer more efficient and effective extraction of bioactive compounds in terms of extraction yield, time, and minimal solvent and energy use. Furthermore, the results showed that the different solvent ratios in the extraction mixture will affect the extraction of bioactive compounds, and a binary solvent system with a combination of methanol and water was the most efficient for the studied compounds in Centella asiatica.

Keywords: Centella asiatica; extraction technique; green technology; microwave; phytochemicals; subcritical water; ultrasound.

Grants and funding

This work was supported by the University of Auckland, which provided research facilities and consumables. The first author is supported by the University Grants Commission of Sri Lanka with financial assistance to do her PhD studies at the University of Auckland.