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

• Published in: Natural product research Vol. 35; no. 23; pp. 5183 - 5191
• Main Authors: Ibrahim, Reham R., Ibrahim, Haitham A., Shabana, Samah S., El-Hosari, Doaa G, Ali, Sahar A., Mahgoub, Shahenda, Moharram, Fatma A.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 02-12-2021; Taylor & Francis Ltd
• Subjects: Acetic acid; Antioxidant; Antioxidants; Ascorbic acid; Calothamnus quadrifidus; Ethyl acetate; flavonoids; Gallic acid; Kaempferol; Myrtaceae; Nitric oxide; NMR; Nuclear magnetic resonance; Phenolic compounds; Phenols; Quercetin; Radicals; Superoxide; tannins; Myrtaceae; tannins; Antioxidant; flavonoids; Calothamnus quadrifidus
• ISSN: 1478-6419; 1478-6427
• DOI: 10.1080/14786419.2020.1789982

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 (
1
H-/
13
C-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.