– Sesquiterpene: A chemosystematic study of eleven species from the genus Lactuca was performed, based on the distributional data for eight sesquiterpene lactones as diagnostic characters (Klaudia et al., 2009). On a study of sesquiterpene lactones, the major components found were oxalate and sulfate derivatives of the guaianolide sesquiterpene lactones (e.g., lactucin, lactucopicrin, and deoxylactucin).
The oxalates were unstable, reverting to the parent sesquiterpene lactone on hydrolysis, whereas the sulfates were stable.
The major components in Lactuca species examined were lactucopicrin 15-oxalate and lactucin 15-oxalate (Bennett et al., 2001).
Another study showed that the major components are 15-oxalyl and 8-sulfate conjugates of the guaianolide sesquiterpene lactones, lactucin, deoxylactucin, and lactucopicrin (Sessa et al., 2000).
Lactuca virosa contained three major sesquiterpene lactones, i.e. lactucin, 8-deoxylactucin, and lactucopicrin (Hajime et al., 1995). A total of 19 sesquiterpene lactones were isolated from roots of Lactuca canadensis including three pairs of zaluzanin C-type guaianolides, epimeric at C-3, and six eudesmanolides, oxygenated at C-1 and C-3 (Klaudia et al., 2013).
From roots of Lactuca georgica 15 sesquiterpene lactone aglycons and glycosides were isolated, including 10 lactucin-type guaianolides. Seven lactucin derivatives esterified at C-8 with acetic, methacrylic and 4-hydroxyphenylacetic acids (Klaudia et al., 2014).
From the roots of Lactuca laciniata (Houtt.) Makino, 7 compounds were isolated, one of them is 11β, 13-dihydrolactucin acetate (Zhiming et al., 1996). Lactucin, 8-deoxylactucin and lactupicrin were detected in both lactuca saligna and Lactuca viscosa (Hajime et al., 1995)
– Phenolic Compounds: The content of phenolic compounds for three species of Lactuca (Lactuca tenerrima, Lactuca virosa and Lactuca muralis) was reported,derivatives of apigenin, luteolin, and quercetin were found, with luteolin 7-O-(6”-O-methyl)-glucuronide being present in Lactuca tenerrima. (Salvador et al., 1994).
From the root tubers of Lactuca tuberosa, nine phenolic compounds were isolated, including two furofuran lignan glucosides, lactuberin A and lactuberin B, belonging to the epi series of 2,6-diaryl-3,7-dioxabicyclo¹octane type furofuran lignans.
The major phenolic constituents of the root tuber of Lactuca tuberosa are caffeic acid, chlorogenic acid and 3,5 dicaffeoylquinic acid (Anna et al., 2013). Scopolin, fraxetin 7-O-β-glucopyranoside (isofraxoside), 4-hydroxyphenylacetic acid, syringic acid, 9α-hydroxyzaluzanin C, its 11β,13-dihydroderivative, ixerin F, 11β,13-dihydroglucozaluzanin C and α-xylofuranosyluracil were identified from Lactuca inermis (Klaudia and Wanda, 2014). (2S)-1-O-Heptatriacontanoyl glycerol, (2S, 3S, 4R, 10E)-2-[(2R)-2-hydroxy- tetracosanoylamino]-10- octadecene-1, 3, 4-triol; 11β, 13-dihydrolactucin acetate, lactucin, lactuside B, lactucopicrin, oleanolic acid, hexadecanoic acid, quercetin, friedelin, ursolic acid and octanedioic acid were identified from rhizome of Lactuca laciniata (Xiang et al., 2014). Seed oils of Lactuca scariola and Lactuca sativa contained epoxy acids at 10.0% (6.0% coronaric + 4.0% vernolic), 27.4% (16.9% coronaric + 10.5% vernolic) and 20.0% (16% coronaric + 4.0% vernolic), respectively, along with normal fatty acids (Ansari et al., 1987).
The aerial parts of Lactuca muralis yielded 2 flavones and caffeic acid derivative, while the roots of the plant afforded 9 sesquiterpene lactones, 5 of which in glycosidic form (Kisiel and Barszcz, 1995). 3,5-Dicaffeoylquinic acid and hydroxycinnamates: caftaric acid, chlorogenic acid and cichoric acid were separated from a hairy root culture of Lactuca virosa (Anna et al., 2012).