Antioxidant and cytotoxic activity of polyphenolic compounds isolated from the leaves of Leucenia leucocephala

Abstract

Context: Cancer is a serious clinical problem to the health care system. Anticancer drugs have been extracted from plants containing phenolic compounds. Leucenia species (Fabaceae) contain a variety of bioactive components of numerous biological and pharmacological properties.

Objective: This study explored the constitutive polyphenols of Leucenia leucocephala Lam. growing in Egypt and evaluated the antioxidant and cytotoxic activity.

Materials and methods: Chemical structures of the isolated compounds from the leaves of L. leucocephala were established by spectral techniques (UV, ¹H, and ¹³C NMR, MS).

Results: Chromatographic separation of 80% MeOH extract of the leaves of L. leucocephala have resulted in a novel flavonoid-galloyl glycoside [myricetin 3-O-(2′,3′4′-tri-O-galloyl)-α-l-rhamnopyranoside] with three known polyphenolic compounds isolated for the first time from this species (apigenin 7-O-β-d-glucuronopyranoside methyl ester, luteolin 7-O-β-d-glucuronopyranoside methyl ester, and 1,3,6-tri-O-galloyl-β-d-glucopyranose) and seven known previously isolated compounds. Also, 80% methanol extract exhibited high antioxidant activity (SC₅₀ = 3.94 µg/ml), which is correlated with its phenolic content. The extract also showed cytotoxic activity against Hep G2 (IC₅₀ value 1.41 µg/ml) confirming its anticancer activity against hepatocellular carcinoma. Among the tested compounds (4–8) for antioxidant property, compound 7 was the most active compound (SC₅₀ = 2.49 µg/ml). Also compounds 7 and 8 exhibited high cytotoxic activity (IC₅₀ = 2.41 and 2.81 µg/ml, respectively).

Discussion and conclusion: These findings demonstrate that the leaves of L. leucocephala contain a considerable amount of polyphenolic compounds with high antioxidant properties, thus it has great potential as a source for natural health products.

Keywords::

• Fabaceae
• Acacia
• flavonoid glycosides
• tannins
• free radical scavenger
• anticancer activity

Acknowledgment

The authors would like to thank the Department of Tumor Biology, National Cancer Institute, Cairo University for hosting the cytotoxicity activity in the department.

Declaration of interest

The authors report no conflicts of interest.