New phenolic compounds from Calothamnus quadrifidus R.Br. aerial parts and their antioxidant activity

Abstract

Two new compounds calothphenone (1) and 6-methoxy kaempferol 3-O-(6″-E-p-coumaroyl)-β-d-glucopyranoside (6-methoxy tiliroside) (2) along with six known compounds viz gallic acid (3), methyl gallate (4), kaempferol 3-O-(6″-E-p-coumaroyl)-β-d-glucopyranoside (tiliroside) (5), castalagin (6), kaempferol (7) and quercetin (8) were isolated from the ethyl acetate fraction (EAF) of 80% aqueous methanol extract of Calothamnus quadrifidus aerial parts. Their structure was established based on different chemical and spectroscopic techniques (¹H-/¹³C-NMR and 2D NMR). Antioxidant activity for EAF and compounds 1, 2 and 5 was evaluated using DPPH, superoxide radical and nitric oxide (NO) inhibition methods. EAF exhibited strong activity to inhibit DPPH, superoxide and NO radicals. Moreover, all tested compounds demonstrated a close high ability to inhibit superoxide and NO radicals in comparison to ascorbic acid, but they exerted lower activity towards DPPH radical.

Keywords:

• Antioxidant
• Calothamnus quadrifidus
• flavonoids
• Myrtaceae
• tannins

Disclosure statement

The authors declare that they have no competing interests.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.