The major components of the white exudates of farina from the abaxial side of the frondsof Cheilanthes argantea are the diterpenoid acids ent-8(17),E-13-labadien-1 oic acid and its3R-hydroxy derivative (Wollenweber et al., 1982).
A kaurane diterpene identified as entkaura16-en-19-oic acid was isolated from the viscid exudates found on fronds of the fernCheilanthes kaulfussi (Wollenweber et al.,1989).
Two sesterterpenes viz. cheilanthatriol (42)(Khan et al., 1971) and cheilarinosin (Iyer et al., 1972) were obtained from Cheilanthesfarinosa. Fern-9(11)-en-3-one was isolated from Cheilanthes longissima (Sunder et al.,1976).
Three triterpenes viz. 6β,22-dihydroxyhopane (43), fernenol and diplopterol (44) inaddition to β-sitosterol-O-β-D-glucoside were isolated from Cheilanthes marantae (Gonzalezet al., 1976) A styrene glycoside (hydroxysteryl-β-D-glucoside) was extracted from Cheilanthes kuhnii(Murakami et al,1980). β-Sitosterol and β-sitosterol glucoside were isolated from Cheilantheslongissima (Sunder et al., 1974).
Farinosyn, an insect growth regulator was isolated from the silver fern Cheilanthesfarinosa (Sivakumar et al., 2003).
Two ecdysone analogs, cheilanthone A (7,8dihydroecdysone) and cheilanthone B (25-deoxy-7,8-dihydroecdysone) were identified fromCheilanthes tenuifolia (Faux et al., 1970).
Cheilanthone B was also identified from Cheilanthes mysurensis (Iyer et al., 1973).
The presence of an unstable carcinogenic glucoside named ptaquiloside, containing a reactive cyclopropane ring has been reported in both Cheilanthes farinosa (Kumar et al., 2001) and Cheilanthes sieberi (Agnew and Lauren, 1991; Potter and Baird, 2000).
Several Cheilanthes species produce farinose exudations, deposited mainly on the under surface of the fronds, consisting of flavonoid aglycons excreted by glandular hairs.
Investigations showed that they were mostly methyl derivatives of apigenin, kaempferol and quercetin (Wollenweber, 1976a).
The flavonoids identified from some Cheilanthes species are shown in Table 3.Kamaya et al. (1993) studied the constituents of Cheilanthes chusana to clarify the relationship between the two genera Cheilanthes and Aleuritopteris from a chemotaxonomic standpoint.
The following constituents were isolated from Cheilanthes chusana: (22R)-cholest-5-ene-3β,7β,22-triol-7,22-bis-O-β-D-glucopyranoside,2-methyl-6-prenylbenzene-1,4-diol-1-O-β-D-glucopyranoside, kaempferol 3-O-rutinoside and quercetin 3-O-rutinoside.
The chemical constituents of Cheilanthes chusana were very different from those of Aleuritopteris species, and therefore, the authors considered that Aleuritopteris species might be separated from Cheilanthes from a chemotaxonomic standpoint.