A new acylated iridoid and other chemical constituents from Valeriana jatamansi and their biological activities

Abstract A new acylated iridoid, valejatadoid H (1), along with fourteen known compounds, were obtained from the n-BuOH extract of the roots and rhizomes of Valeriana jatamansi, and their structures were elucidated by various spectroscopic methods. Among them, compounds 8, 11 and 13 exhibited potent inhibition on NO production, with IC50 values of 4.21, 6.08 and 20.36 μM, respectively. In addition, compounds 14 and 15 showed anti-influenza virus activities, among which compound 14 exhibited significant effect with an IC50 value of 0.99 μM. Graphical Abstract


Introduction
The genus Valeriana (family Caprifoliaceae) is abundant in species and widely used in traditional medicine. Valeriana plants are mostly used as sedative and hypnotic drugs with definite curative effect and without toxic and side effects (Bach et al. 1993;Ming et al. 1997;Tang et al. 2002;Dong et al. 2015;Zhang et al. 2017;Maurya et al. 2020). Valeriana jatamansi Jones, a representative medicinal plant of the genus Valeriana, is distributed widely in southwestern areas of China (Ming et al. 1997). As an important substitute of V. officinalis, V. jatamansi has been proved to have neuroprotective (Tang et al. 2002;Yu et al. 2005;Lin et al. 2010a;Xu et al. 2011Xu et al. , 2012Tian et al. 2019), sedative-hypnotic (Bach et al. 1993;Ming et al. 1997;Tang et al. 2002;Chen et al. 2005) and antiviral effects (Ming et al. 1997;Murakami et al. 2002;Tang et al. 2002). Phytochemical investigation on V. jatamansi reported the isolation of iridoids, sesquiterpenoids, lignans, flavones, volatile oils, and so on (Ming et al. 1997;Lin et al. 2010aLin et al. , 2010bDong et al. 2015;Liu et al. 2021).

Biological studies of compounds
The effects of compounds 1-15 on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated RAW 264.7 cells were evaluated. N G -monomethyl-L-arginine monoacetate salt (L-NMMA) was used as positive control (IC 50 ¼ 20.75 lM). The results (Table S2 in the Supplementary Material) showed that compounds 8, 11 and 13 possessed potent inhibitory effects, with IC 50 values of 4.21, 6.08 and 20.36 lM, respectively, but their cytotoxicity could not be ignored, with CC 50 values of 12.37, 11.52 and 34.54 lM, respectively.
RAW 264.7 cells and L-NMMA were purchased from Conservation Genetics CAS Kunming Cell Bank, Kunming, China (No. KCB200603YJ) and Beyotime Institute of Biotechnology, Shanghai, China, respectively. MDCK cells were kindly provided by Dr. Fan Yang, Kunming University of Science and Technology. Oseltamivir were purchased from Saen Chemical Technology Co., Ltd., Shanghai, China.

Plant materials
The dried roots and rhizomes of Valeriana jatamansi Jones were purchased from Luosiwan Chinese herbal medicine market, Kunming, China, in June 2017, and identified by Dr. Jin-Dong Zhong, Kunming University of Science and Technology. The voucher specimen (KMUST 20170601) was deposited at the Laboratory of Phytochemistry, Faculty of Life Science and Technology, Kunming University of Science and Technology.

No production assay
RAW 264.7 cells were cultured in Dulbecco's Eagle's Medium (DMEM) (GIBCO) medium supplemented with 10% (v/v) fetal bovine serum (FBS), 1% penicillin (10,000 U/mL)streptomycin (10,000 lg/mL) and 10 mM HEPES in a 37 C, 5% CO 2 cell incubator. Inhibition of NO production assay was carried out as described previously (Cao et al. 2016;Lee et al. 2016). Cells were pre-treated with compounds 1-15 at concentrations of 3.125-50 lM, and co-incubated with 1 lg/mL LPS for 24 h. The absorbance was measured in a microplate reader at 540 nm (Thermo Fisher Scientific, MA, USA). DMSO and L-NMMA were used as negative and positive control, respectively. Cell viability was detected by MTT assay. IC 50 values were calculated by IBM SPSS Statistics 20. All experiments were performed in triplicate.

Anti-influenza virus assay
Influenza strains A/WSN/33/2009 (H1N1) was used in this study. Oseltamivir was used as positive control. MDCK cells were maintained in DMEM supplemented with 10% (v/ v) FBS, 1% penicillin (10,000 U/mL)-streptomycin (10,000 lg/mL), along with 10 mM HEPES in a 37 C, 5% CO 2 incubator. Assessment of anti-influenza virus activity was performed as described previously (Dang et al. 2014). IC 50 values were calculated by IBM SPSS Statistics 20. All experiments were performed in triplicate.

Conclusion
In brief, fifteen compounds, including a new acylated iridoid, valejatadoid H (1), were isolated from the n-BuOH extract of the roots and rhizomes of Valeriana jatamansi, and the structure of compound 1 was elucidated by various spectroscopic methods. Among them, compounds 13 and 15 were isolated from the family Caprifoliaceae for the first time, while compounds 3, 9 and 10 were obtained from the genus Valeriana for the first time. In addition, compounds 8, 11 and 13 exhibited potent inhibitory effects on NO production, while compound 14 showed significant anti-influenza virus activity.

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

Funding
This work was financially supported by the National Natural Science Foundation of China (Nos. 32060106 and 31560103) and Applied Basic Research Foundation of Yunnan Province (No. 2019FB025).