Volatile and aroma profiling of flower and rhizome of Hedychium flavescens growing in North Western Himalayan region

Abstract The present investigation was carried out for a comparative volatile study and aroma profiling of Hedychium flavescens. The headspace gas chromatography mass spectrometry (GC-MS) analysis of flowers (HS-F) and rhizome (HS-R); GC-MS analysis of flower essential oil (EO-F), flower absolute (AB-F) and rhizome essential oil (EO-R) revealed 27, 19, 19, 15 and 12 compounds which constitute 96.22%, 96.93% 97.43%, 86.79% and 97.62% composition, respectively. The identification results demonstrated that flowers and rhizome were rich in β-pinene, 1,8-cineol, linalool and E-β-caryohyllene components. β-Pinene was the most abundant component in HS-R (38.99%), EO-R (26.61%); linalool in HF-F (25.34%) and EO-F (25.99%) and ρ-vinyl-guaiacol in AB-F (32.19%), respectively. The aroma profile of H. flavescens was dominated with floral and jasmine (flowers); spicy, earthy and herbal (EO-F); floral and balsamic (AB-F); herbal, pungent, spicy and earthy (rhizome and EO-R) notes. Based on aroma profile, AB-F was evaluated as potential ingredient for perfume industry. Graphical Abstract


Introduction
Hedychium species (family Zingiberaceae) commonly known as ginger lilies, is widely distributed in the tropical and sub-tropical regions of India, China and South East Asia (Ray et al. 2019). The genus has about 80 different species in South Asia, of which 14 are endemic to India. These species are perennial rhizomatous herbs with mostly distinct dormancy periods and flowering once a year during monsoon. Rhizomes are thick, fleshy and aromatic; and its extract is used for various medicinal purposes like eye infection (Ray et al. 2018). Hedychium species are cultivated for its essential oil as a source of natural perfumes (Suksathan et al. 2014;Ray et al. 2019).
Although there have been studies regarding chemical analysis of EO from H. flavescens rhizome (Ray et al. 2018), the flowers have not been explored yet in this context. In continuation of our studies on Himalayan Bioresources (Joshi and Gulati 2015;Maurya et al. 2021), this report presents aroma profiling and a valuable comparative study between volatiles of HS-F, EO-F, AB-F, HS-R and EO-R.
The volatile component analysis revealed that linalool was the most common and prominent component in HS-F, EO-F and AB-F followed by E-b-caryophyllene. b-Pinene was detected with abundance in HS-F (19.0%) and EO-F (15.36%), but was missing in AB-F. Although q-vinyl-guaiacol was detected as most abundant component (32.19%) in AB-F but it was detected as minor component (0.27%) in HS-F and was undetected in EO-F. Hexadecane (6.2%), tetradecane (4.17%), tridecane (3.72%), E,E-geranyl linalool (3.18%), ethyl-9-octadecenoate (2.36%), pentadecane (2.25%), eugenol (2.08%), heptadecane (1.51%), octadecane (1.92%) were detected only in AB-F and were undetected in both HS-F and EO-F. E-b-Caryophyllene was detected with significant amount in HS-F (15.09%) and EO-F (15.35%) and with small amount in AB-F (4.04%). Surprisingly, it was observed that components like b-pinene, a-pinene, E-b-ocimene, 1,8-cineol and other monoterpene hydrocarbons were detected with a significant amount in HS-F and EO-F but were absent in AB-F. This may be due to the loss of highly volatile monoterpene hydrocarbons and oxygenated monoterpenes during the extraction and drying process of the AB-F.
The volatile component analysis of rhizome part revealed that b-pinene was the most prominent compound in HS-R (38.99%) and EO-R (26.61%). 1,8-Cineol, a-pinene, linalool, c-terpinene, terpinen-4-ol and a-phellandrene were also detected at significant amount in HS-R and EO-R. Camphene, b-phellandrene, b-myrcene, a-terpineol and a-terpinene were detected in HS-R but not in EO-R. Some components like q-cymene, limonene (2.45%), terpinen-4-ol (1.66%), bornyl acetate (0.42%) and d-elemene (0.39%) were detected only in EO-R. In terms of chemical composition, our study was in good agreement with previous studies (Sakhanokho et al. 2013;Ray et al. 2018). Surprisingly, sesquiterpene hydrocarbons like b-elemene, a-guaiene, seychellene, Eb-farnesene, (E,E)-a-farnesene, d-guaiene; and oxygenated sesquiterpene like patchouli alcohol were detected in HS-R but were absent in EO-R. This may be due to loss during hydro-distillation process. Among all extraction and analytical techniques, the headspace GC-MS technique revealed more variety of compounds in comparison to solvent extraction and hydro-distillation technique.
These results revealed that flowers and rhizome were rich in b-pinene, 1,8-cineol, linalool and E-b-caryophyllene components. These molecules have reported analgesic, antimicrobial, anti-inflammatory, antioxidant and anticancer activities. Aromatic plants containing these molecules in abundance have enormous application in pharmaceutical, cosmetic and perfumery industry (Ray et al. 2018;Palariya et al. 2019). Linalool being a major floral scent in nature is a widely used ingredient in perfumery and cosmetic industry. It is also reported to have sedative and anxiolytic activities, which highlights its potential in aromatherapy (Aprotosoaie et al. 2014).

Aroma profile
To differentiate between aroma of flowers, rhizome and their extracts; their aroma profiles were generated on the basis of sensory analysis. The aroma profile of flowers was dominated with floral (3), jasmine like (2.5), woody (1), spicy (0.5) and balsamic (1.5) notes ( Figure S1). Aroma profile of EO-F was dominated with spicy (3), earthy (2.5), herbal (3) and floral (1.5) notes. In case of AB-F, aroma profile was dominated with floral (2), jasmine like (1), woody (1.5), spicy (2) and balsamic (2.5) notes. It was observed that aroma profile of AB-F was comparable to flowers whereas aroma profile of EO-F was very different from flowers. The aroma difference was also observed during sensory analysis of their parent samples. In case of rhizome, the aroma profile was dominated with herbal (2), spicy (1.5), woody (1), pungent (2.5) and earthy (2) notes ( Figure  S2). In case of EO-R, the aroma profile was dominated with herbal (2.5), spicy (1.5), camphory (1), citrus (1), pungent (2) and earthy (1.5) notes. In a previous study, the aroma profile of rhizome essential oil from Zingiber montanum (family Zingiberaceae) was dominant with camphory, spicy, warm and sweet notes (Bora et al. 2021). In this study terpinen-4-ol was determined as key odorant of rhizome essential oil and contributes camphory and spicy notes to the oil (Bora et al. 2021). Terpinen-4-ol was detected only in EO-R in our study and its reported odor was in good agreement with aroma profile of EO-R. The aroma profile of fresh rhizome and EO-R were very similar, which was also observed during sensory analysis.

Application of flower absolute (AB-F)
Based on sensory analysis and aroma profiling it was observed that the AB-F has pleasant floral and jasmine like fragrance notes which can be formulated into a high grade natural perfume. According to blending perception, it was blended with top notes (Bergamot and Sweet Orange), middle notes (Neroli, Geranium and Pine) and base notes (Ylang-ylang, Frankincense, Cedarwood, Vanilla and Cinnamon). After olfactory test among panelists and students, fixatives like benzoin was added and the formulation was diluted with perfumer's alcohol to make a high grade, long lasting unisex perfume that could be described as floral, spicy and balsamic.

Conclusion
The current study reports on aroma profiling and a valuable comparison between volatiles from HS-F, EO-F, AB-F, HS-R and EO-R. The identification results demonstrated that flowers and rhizome were rich in monoterene hydrocarbons and oxygenated monoterpenes like a-pinene, b-pinene, 1,8-cineol and linalool components. b-Pinene was most abundant in HS-R and EO-R whereas linalool was most abundant in HS-F and EO-F. AB-F was abundant with a different component q-vinyl-guaiacol. The abundance of these important bioactive and fragrant molecules makes this weed a potential source for pharmaceutical and cosmetic industry. The aroma profile of H. flavescens was dominated with floral and jasmine like (flowers); spicy, earthy and herbal (EO-F); floral and balsamic (AB-F); herbal, pungent, spicy and earthy (rhizome and EO-R) notes. Based on sensory analysis and aroma profiling of flowers, rhizome and their extracts, the flower absolute of H. flavescens (AB-F) had been formulated into a high grade perfume and presented as potential ingredient for perfume and cosmetic industry.

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