New biphenyl derivatives and anti-inflammatory constituents from the stem bark of Magnolia officinalis

The stem bark of Magnolia officinalis Rehd. et Wils. (Magnoliaceae) has been used as a traditional medicine for the treatment of gastrointestinal disorders, bronchitis, and emphysema, in China, Taiwan, Japan, and Korea [1]. Chemical studies have revealed a variety of neo-lignans and alkaloids as constituents of this plant. Many of these compounds exhibit central depressant effect, muscle relaxation, and antigastric ulcer, antibacterial, antiallergic, vasorelaxant, and neurotrophic activities. Investigation on EtOAc-soluble fraction of the stem bark of M. officinalis has led to the isolation of three new biphenyls, 5-allyl-5'-(1-hydroxyallyloxy)biphenyl-2,2-diol (1), 5,5'-diallyl-2'-(allyloxy)biphenyl-2-ol (2), and 5,5'-diallyl-2'-(3-methylbut-2-enyloxy)biphenyl-2-ol (3), together with 12 known compounds, including four neolignans, magnolol (4), honokiol (5), (-)-monoterpenylmagnolol (6), and randainal (7), two norlignans, magnaldehyde D (8) and randaiol (9), and six steroids, β-sitostenone (10), stigmasta-4,22-dien-3-one (11), β-sitosterol (12), stigmasterol (13), 3β-hydroxystigmast-5-en-7-one (14), and 3β-hydroxystigmasta-5,22-dien-7-one (15). The structure of new compounds (1-3) were determined through spectroscopic and MS analyses. Among the isolates, magnolol (4) and honokiol (5) exhibited potent inhibition against fMLP-induced superoxide production with IC₅₀ values of 4.42±0.24 and 0.68±0.20µg/mL, respectively. In addition, magnolol (4) inhibited fMLP/CB-induced elastase release with an IC₅₀ values of 1.45±0.20µg/mL.

Figure 1: Structures of new compounds 1–3

Acknowledgement: This research was supported by grants from the National Science Council of the Republic of China (NSC 95–2320-B-127–001-MY3 and NSC 98–2320-B-127–001-MY3), awarded to Prof. J.-J. Chen.

References: 1. Xia NH et al. (2008) 'Magnoliaceae' in 'Flora of China', Science Press, Beijing. Vol. 7, pp. 48–91.