Two new phenol compounds from roots of Ardisia crenata

Abstract Two new phenols, ardisiphenol I (1) and ardisiphenol J (2), along with three known compounds (3-5) were isolated and identified from the roots of Ardisia crenata var. bicolor. Their structures were elucidated by means of spectroscopic techniques. Structurally, new compounds 1 and 2 have rare side chain with seven carbons. All compounds were tested for antibacterial activity, and compound 5 showed moderate antibacterial activity against Enterococcus faecalis. This work provided the isolation and structural identification of all the compounds in detail, and shed a new light on its further research. Graphical Abstract


Introduction
The species Ardisia crenata belongs to the family Myrsinaceae (Kitajima et al. 2006;Hu et al. 2020). The roots and leaves of Ardisia crenata var. bicolor, named 'Hong Liang San' in the Miao medicine, were widely used in the treatment of infectious diseases (Liu et al. 2007(Liu et al. , 2009. Previously, a large number of different types of compounds are isolated from different parts of A. crenata, including isocoumarins (Jia et al. 1995), triterpenoid saponins (Zheng et al. 2008;Liu et al. 2016), benzoquinones (Podolak et al. 2021) and phenol derivatives (Song et al. 2021 PRODUCT RESEARCH 2023, VOL. 37, NO. 19, 3306-3309 https://doi.org/10.1080/14786419.2022 have been intensively reported, and few reports focus on its phenolic components. In continuation of our works on valuable natural molecules (Wei et al, 2021), ardisiphenol I (1) and ardisiphenol J (2), two new phenols along with three known compounds (3-5) were isolated and identified from the roots of A. crenata var. bicolor (Fig 1.). Their structures were elucidated by means of spectroscopic techniques. Structurally, new compounds 1 and 2 have rare side chain with seven carbons. Compounds 1-5 were evaluated for antibacterial activity against four bacteria strains at a concentration of 0.2 mg/mL. Compound 5 showed moderate antibacterial activity against Enterococcus faecalis with a 10.1 mm bacteriostatic circle diameter (Supporting Information Figure  S2). Herein, this work provided the isolation, structural identification, and biological activity evaluation of all the compounds in detail, and shed a new light on its further research.

Results and discussion
Compound 1 was obtained as yellow oil.   Table S1). All of these data suggested that compound 1 may be a meta-trisubstituted phenol derivative with a seven carbons side chain (Chang et al. 2009    ESI-MS experiment. Compound 2 had similar 1 H NMR and 13 C NMR signals with compound 1 except for one more methyl chemical shift at d C 8.9 and the signal disappearance of H-4 in 1. In the HMBC spectrum of 2, the correlations from the methyl proton at [d H 2.08 (3H, s, CH 3 -C 4 )] to the quaternary carbon at d C 119.9 (C-4) established the existence of C-4 methyl group. Based on the above evidence, new compound 2 was named ardisiphenol J and elucidated as shown in figure 1.
Compounds 1-5 were evaluated for antibacterial activity against four bacteria strains at a concentration of 0.2 mg/mL. Compound 5 showed moderate antibacterial activity against E. faecalis with a 10.1 mm inhibition diameter (Supporting Information  Table S2).

Conclusions
In summary, ardisiphenol I (1) and ardisiphenol J (2), two new phenols along with three known compounds (3-5) were isolated and identified from the roots of A. crenata var. bicolor (Fig 1.). Structurally, new compounds 1 and 2 have rare side chain with seven carbons. Compounds 1-5 were evaluated for antibacterial activity against four bacteria strains at a concentration of 0.2 mg/mL. Compound 5 showed moderate antibacterial activity against E. faecalis (Supporting Information). This work provided the isolation, structural identification, and biological activity evaluation of all the compounds in detail, and shed a new light on its further research.

Disclosure statement
No potential conflict of interest was reported by the authors.