Absolute stereochemistry and anti-inflammatory activity of cycloisobrachycoumarin, brachycromone, cyclobrachycoumarin, and cyclobrachycoumarin 2’-epimer from Gerbera delavayi

• Published in: Phytochemistry letters Vol. 61; pp. 135 - 141
• Main Authors: Yang, Yong-xun, Wang, Qun, Li, Xiao-nian, Huang, Hai-yan, Geng, Hao
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2024
• Subjects: 5-Methyl-4-hydroxycoumarin-monoterpene hybrids; Absolute stereochemistry; Anti-inflammatory activity; Gerbera delavayi; 5-Methyl-4-hydroxycoumarin-monoterpene hybrids; Absolute stereochemistry; Anti-inflammatory activity; Gerbera delavayi
• ISSN: 1874-3900; 1876-7486
• DOI: 10.1016/j.phytol.2024.04.011

Four isomeric 5-methyl-4-hydroxycoumarin-monoterpene hybrids (MMHs) comprising three known MMHs, cycloisobrachycoumarin (1), brachycromone (2), cyclobrachycoumarin (3), and a new epimer of 3, cyclobrachycoumarin 2’-epimer (4) were isolated from Gerbera delavayi. The absolute configuration of 1–4 was elucidated by utilizing ECD calculations and X-ray diffraction analysis. As a result, the absolute configurations of C-2’ and C-3’ in 1 and 2 were revised to be 2′S, 3′R and 2′R, 3′S respectively. Consequently, the diagnostic negative/positive cotton effect (CE) at around 210–220 nm for the stereochemistry of angular/linear furano-MMHs is discussed and formulated. Moreover, compounds 1–4 were tested for the nitric oxide (NO) inhibitory activity by using lipopolysaccharide (LPS)-induced RAW 264.7 cells in vitro. The results showed that 1–4 significantly inhibited NO production at the concentration of 10.0 μM, indicating that 1–4 possessed potent anti-inflammatory activity. [Display omitted] •Four isomeric MMHs (1−4) including a new one (4) were isolated from Gerbera delavayi.•The absolute configurations of cycloisobrachycoumarin (1) and brachycromone (2) were revised.•For angular furano-MMHs, the diagnostic CE is correlated with the orientation of the biggest group at β-C or γ-C.•For linear furano-MMHs, the diagnostic CE is correlated with the orientation of the big group at β-C.•Compounds 1–4 possessed potent anti-inflammatory activity.