Uncommon secondary metabolites from Etlingera pavieana rhizomes

Abstract From the rhizomes of Etlingera pavieana (Pierre ex Gagnep.) R.M. Sm., four phenylpropens, (E)-3-(4-methoxyphenyl)prop-2-en-1-amine (1), (E)-4-methoxycinamaldehyde (2), (E)-4-methoxycinamic acid (3) and (E)-1-methoxy-4-(3-methoxyprop-1-enyl)benzene (4), together with two other compounds, (E)-((E)-3-(4-methoxyphenyl)allyl)3-(4-hydroxyphenyl)acrylate (5) and 4-methoxybenzoic acid (6) were isolated. This is the first report on the presence of all compounds in Etlingera. Compounds 1 and 5 have been previously synthesised, but this is the first report of their isolation from a natural source. Compound 5 exhibited weak activity against Mycobacterium tuberculosis with MIC 50.00 μg/mL and cytotoxic activity against the KB, MCF7 and NCI-H187 cells with IC50 values of 25.11, 20.16 and 34.83 μg/mL, respectively.

2014; Hartati et al. 2014;Kumar et al. 2014;Marrelli et al. 2015;Semwal et al. 2015;Tundis et al. 2015). Etlingera pavieana (Pierre ex Gagnep.) R.M. Sm. belongs to the Zingiberaceae family which is native to Indonesia, Malaysia and Thailand. It is an aromatic plant and used as traditional medicine to treat dyspepsia, nausea, diuretic, fever and cough and as carminative in Thailand. The ethyl acetate subfractions of E. pavieana were reported to exhibit anti-inflammatory activities through the suppression of NO without cytotoxic effect (Inrod, 2008). So far there have been no reports regarding phytochemical study of this plant except for a report on chemical components in the essential oil (Tachai et al. 2014). However, previous phytochemical investigations on the genus Etlingera have revealed the presence of diarylheptanoids, labdane diterpenes and sterioids from rhizomes of E. elatior ; phenolic compounds from rhizomes of E. littoralis (Jeerapong et al. 2011) and steroids from leaves and stems of E. brevilabrum (Mahdavi 2014). In this study, the chemical constituents of the CH 2 Cl 2 extract of the rhizomes of E. pavieana was examined and six compounds were obtained. Antimycobacterial activity against Mycobacterium tuberculosis and cytotoxicity against KB, MCF7 and NCI-H187 cells of the extracts and compounds was evaluated. These compounds are known, but they were isolated from this plant for the first time.
Compounds 1 and 5 have been reported previously as synthetic compound (Hu et al. 2005;dewal et al. 2012;Ji et al. 2013;Yin et al. 2014) and this is the first time that they were isolated from natural source. Besides, there has been no report regarding their biological activity. Compound 2 was previously reported to be isolated from Piper philippinum (Chen et al. 2007). It was potentially a useful antipathogenic lead compound for treatment of vibriosis (Brackman et al. 2008) and was reported to inhibit RSV-induced cytopathy (wang et al. 2009). Compound 3 was originally reported from Arachis hypogaea , Scrophularia buergeriana Miquel (Lee et al. 2002;Park et al. 2010) Aquilegia vulgaris (Bylka 2004) and Anigozanthos preissii (Hidalgo et al. 2015). It showed significant hepatoprotective activity (Lee et al. 2002), anti-amnesic , cognition-enhancing activity (Kim et al. 2003), antihyperglycemic (Adisakwattana et al. 2005) and neuroprotective activities Park et al. 2010). Compound 4 was isolated from Morina chinensis (Su et al. 1999). Compound 6 has been reported previously from Capparis spinosa (Gadgoli & Mishra 1999) and Cistus ladanifer (Chaves et al. 2001). It was reported to possess significant antihepatotoxic activity against carbon tetrachloride and paracetamol induced hepatotoxicity in vivo (Gadgoli & Mishra 1999).

Conclusion
we report the phytochemical study of E. pavieana and demonstrated the antimycobacterial and cytotoxic activities of the n-hexane, CH 2 Cl 2 , methanolic and essential oil extracts as well as of some isolated compounds. The occurrence and biological activities of compounds 1 and 5, two uncommon secondary metabolites were reported here at first. All compounds were identified from this plant for the first time and have not been isolated from any species of Etlingera.

Acknowledgement
This work was financially supported by Rajamangala University of Technology Tawan-Ok and Centre of Excellence for Innovation in Chemistry (PERCH-CIC).

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