Chemical profile, antiproliferative and antioxidant activities of rhizome oil of Zingiber anamalayanum from Western Ghats in India

Abstract Volatile oil from fresh rhizomes of Zingiber anamalayanum was isolated by hydrodistillation and characterised by GC–FID and GC–MS. Twenty-one out of 24 constituents comprising 99.47% of the oil were identified. Major components in Z. anamalayanum rhizome oil were δ-2-carene (52.83%), camphene (9.83%), endo-fenchol (9.42%), iso-dihydrocarveol (6.44%) and cis-p-mentha-2,8-dien-1-ol (5.19%). Monoterpene hydrocarbons in the rhizome oil were 65.81%, followed by oxygenated monoterpenes (23.78%) and sesquiterpene hydrocarbons (9.87%). Physical parameters of rhizome oil were 1.4031, − 16.097o (c = 1, CHCl3) and 0.9202. Z. anamalayanum rhizome oil showed significant anti-Dalton’s Lymphoma Ascitic activity.


Introduction
Genus Zingiber Boehm. of Zingiberaceae family is one important group of rhizomatous herbs constituting spices, herbals and ornamentals. The term 'Zingiber' is derived from the Sanskrit term 'Shringavera' meaning 'horn-shaped' , referring to the protrusions on their rhizomes. The genus comprises over 90 species distributed in tropical and subtropical regions in Southeast Asia (Sabu 2006;Ali et al. 2008). Zingiber officinale is the commercial ginger species best known for its ethnomedical, pharmacological activities and spice value (Ravindran & Babu 2005;Sabu 2006;Ali et al. 2008;Singh et al. 2008;Sasidharan et al. 2012;Marrelli et al. 2015). Zingiberene and ar-curcumene are the major volatile constituents in Z. officinale rhizomes (Afzal et al. 2001). Z. officinale rhizome oil is used in beverage and fragrance industries (Sakamura et al. 1986). Zingiber zerumbet rhizomes are used as flavourings in cooking and are traditionally used as a decoction for relieving stomach ache, as an anaesthetic for tooth ache and for the treatment of swellings, strains, bruises and cuts (Duñg et al. 1993;Lechat-Vahirua et al. 1993). Zerumbone is the major constituent in the rhizome oil of Z. zerumbet (Sabulal et al. 2009). It is a sesquiterpene with potential anticancer, anti-inflammatory, anti-HIV and other biological activities (Sabulal et al. 2009). We recently reported chemical profiles of the rhizome volatile oils of two endemic ginger species, Zingiber nimmonii and Zingiber neesanum, from south India (Sabulal et al. 2006;Sabulal et al. 2007). β-Caryophyllene and α-humulene were the major constituents in Z. nimmonii rhizome oil and phenylbutanoids were the major components in Z. neesanum rhizome oil (Sabulal et al. 2006;Sabulal et al. 2007). Major constituents in Zingiber montanum (Zingiber cassumunar) rhizome oil were terpinen-4-ol and the phenylbutanoid, (e)-l-(3,4-dimethoxyphenyl)buta-1,3-diene (Bordoloi et al. 1999;Sabulal et al. 2007;Bua-in & Paisooksantivatana 2009;Sabulal et al. 2009).
Zingiber anamalayanum Sujanapal & Sasidh. is a recently discovered species from the southern Western Ghats in India. It is a sturdy herb of 75-170 cm tall with a basal cylindrical spike, sparsely distributed in high-altitude grasslands and edges of woodlands (Sujanapal & Sasidharan 2010). Z. anamalayanum is a perennial, rhizomatous herb and its rhizomes are thick, fleshy, yellowish and aromatic with many roots. Here, we report (i) the chemical composition of essential oil from fresh rhizomes of Z. anamalayanum and (ii) its antioxidant and antiproliferative activities.

Conclusions
This is the first report of the chemical composition of the rhizome volatile oil of the rare ginger, Z. anamalayanum. On in vitro cytotoxicity assay, rhizome oil showed significant anti-DLA activity.

Supplementary material
experimental details relating to this article are available online, alongside Tables S1 and S2.

Acknowledgement
AK is thankful to Department of Science and Technology, Government of India for INSPIRe fellowship (No. IF 130643).