Volatile composition of the laksa plant (Polygonum hydropiper L.), a potential source of green note aroma compounds

Volatile compounds were extracted from laksa plant (Polygonum hydropiper L.) by three isolation techniques—dynamic headspace sampling, simultaneous distillation and extraction (SDE) and liquid–liquid extraction with dichloromethane (DCM). In the GC–MS analysis of the volatile extracts, a total of 46 compounds were identified, including 14 carbonyls, 14 alcohols, 10 hydrocarbons, four esters, two furans, one acid and one base. Carbonyls (aldehydes/ketones) and alcohols are the predominant classes of volatile compounds, accounting for almost 90% (or above) of the total volatiles extracted from the plant. The major compounds include dodecanal (3–40%), (E)-2-hexenal (20–35%), decanal (4–22%), (Z)-3-hexen-1-ol (4–31%), hexanal (1.7–5.1%) and β-caryophyllene (1.7–2.3%). Significantly high levels of both (E)-2-hexenal (leaf aldehyde) and (Z)-3-hexen-1-ol (leaf alcohol) may make the weed plant become a potential source of green note aroma componds. More (Z)-3-hexen-1-ol was found in the stem while more (E)-2-hexenal was detected in the leaf. The laksa stem appeared to contain more decanal and dodecanal but less esters than the leaf. Different isolation techniques produced volatile extracts with different proportions of the major volatile components.