Volatiles from leaves of field‐grown plants and shoot cultures of Gynura bicolor DC

Abstract

Systematic investigations of the volatiles of fi eld-grown plants and shoot cultures of Gynura bicolor have been conducted to obtain indispensable plant physiological information for propagating plants of consistent quality. Volatiles obtained by solvent-assisted fl avour evaporation (SAFE) of solvent extracts from leaves of commercial cultivars, shoot cultures and their regenerates were analysed using gas chromatography (GC), GC-mass spectrometry (GC-MS) and GC-olfactometry (GC-O). It was revealed for the fi rst time that this plant had the following chemical characteristics: fi eld-grown plants, i.e. those plants commercially cultivated in three diff erent regions of Japan and 7 month-old regenerates of shoot cultures had almost the same GC profi les; their major components were (E)-caryophyllene, α-humulene and bicyclogermacrene; in contrast, the major components of the shoot cultures were (Z,E)-α-farnesene, (E)-caryophyllene and α-copaene. The biosynthetic pathways for the sesquiterpenes found in these materials were presumed from the analytical results. Aroma evaluations using GC-O revealed that 1-octen-3-one, (Z)-1,5-octadien-3-one and trans-4,5-epoxy-(E)-2-decenal were aroma-impact compounds contributing to the characteristic metallic, green aroma, especially in the shoot cultures. In addition to these results, it was found that 2-isopropyl-and 2-isobutyl-3-methoxypyrazines were additional compounds related to the green, earthy aroma in the regenerates. These aroma-impact compounds were detected only because of the GC-O analysis.

New eudesmane‐type sesquiterpenoids and other volatile constituents from the roots of Gynura bicolor DC.

“…Among them, abundant methoxypyrazines were di‐substituted pyrazines, 2‐methoxy‐3‐isopropylpyrazine ( 10 ) and 2‐methoxy‐3‐ sec ‐butylpyrazine ( 11 ),[43] whose contents in the field‐grown plant roots used in this study were estimated to be 120 ng/g and 230 ng/g, respectively, by GC (FID) analyses using commercial standards. Although the isomer of 11 , 2‐methoxy‐3‐isobutylpyrazine,[44] was one of components contributing to the earthy and bell pepper‐like aromas of leaves of field‐grown plants,[7] this compound could not be detected in the field‐grown plant roots, even with GC‐O. The aroma threshold value (in water) of 10 is reported to be 1–2 pg/g and its aroma characteristics are reported to be bell pepper‐like and earthy.…”

“…Interestingly, these tri‐substituted pyrazines were not found in the leaves of field‐grown plants and shoot cultures, even with GC‐O. [7]…”

“…Additionally, GC‐MS and GC‐O analyses revealed that four methoxypyrazines contributed to the characteristic green, moldy, and earthy aromas of the field‐grown plant roots. In our previous report,[7] 2‐methoxy‐3‐isobutylpyrazine contributed to the characteristic aromas of the leaves of field‐grown plants. However, this di‐substituted methoxypyrazine was not found in the field‐grown plant roots used in this study, whereas its isomer, 2‐methoxy‐3‐ sec ‐butylpyrazine, was present as a major methoxypyrazine.…”

“…[4–6] In our previous phytochemical investigation of the leaves of field‐grown plants and shoot cultures, a number of sesquiterpene hydrocarbons and aroma impact compounds were reported. [7] However, to our knowledge no phytochemical investigation has yet been reported on the volatile constituents of G . bicolor roots, possessing characteristic green, moldy, and earthy aromas.…”

Phytochemical investigation ofGynura bicolorleaves and cytotoxicity evaluation of the chemical constituents against HCT 116 cells

“…The aerial parts are often consumed and believed to confer a wide range of benefits such as anti-cancer, anti-hyperglycaemic, antioxidant and anti-inflammatory effects (Hayashi et al 2002;Li et al 2009;Lu et al 2012;Wu et al 2013 post-labour recovery, blood circulation improvement, treatment of dysmenorrhea and haemoptysis (Li 2006). Previous phytochemical analysis of G. bicolor leaves revealed the presence of sesquiterpenes, anthocyanins, flavonols and megastigmane-type norisoprenoids (Shimizu et al 2009(Shimizu et al , 2010Lu et al 2010;Chen et al 2012). Some people had used G. bicolor to treat colon cancer, and based on our previous findings (Teoh et al 2013), the leaves of G. bicolor possessed cytotoxicity and induced apoptotic and necrotic cell death in human colon carcinoma cells (HCT 116).…”