Flavones and phenylpropenoids in the surface exudate of Psiadia punctulata
Three flavones including 1, along with a docosyl coumarate were isolated from the aerial exudate of Psiadia punctulata. The structures were established on the basis of spectroscopic information and comparison with published data.
Introduction
The leaves of Psiadia punctulata (DC) Vatke are extensively covered by an exudate, especially when young. The exudate is most likely responsible for the unpalatability (to herbivores) and drought resistance (as we have observed) which is exhibited by this shrub, in a manner comparable to that described for Larrea spp. (Rhoades, 1977). The chemistry of the exudate could also explain the use of the species for relief of fever and abdominal pains (Kokwaro, 1976) as well as its use for expunging ectoparasites from cattle (Beentje, 1994).
In an earlier communication we described the presence of kaurene and trachyloban diterpenes in the exudate (Midiwo et al., 1997). We compared these metabolites with the diterpenes reported from P. arabica Jaub and Spach, with which P. punctulata is sometimes confused (Abou-Zaid et al., 1991), and suggested that there were differences which could be used to delineate them as distinct taxa.
Plant leaf exudates are known to most often contain mixtures of terpenoids and non-polar flavonoids (Wollenweber, 1988). In this paper we report on the isolation and characterisation of five flavones, three of which are new, along with two geometrically isomeric phenylpropenoid docosyl esters, one of which has not been reported before.
Section snippets
Results and discussion
Fresh leaves of P. punctulata were dipped in ethyl acetate for short periods (ca. 20 s) providing a gummy extract on removal of solvent. We have established (see Experimental) that the average exudate to dry leaf weight is about 1:4. TLC analysis of the extract revealed seven major spots of phenolic nature (254 nm UV light, ferric chloride spray reagent). Silica gel chromatography led to the successful isolation and characterization of five flavones and two phenylpropenoids.
The first compound (1
General
Mps: uncorr. Analytical TLC: Merck pre-coated silica gel 60 F254 plates. CC on silica gel 60 (70–230 mesh). EIMS: direct inlet, 70 eV. 1H NMR (500 MHz) and 13C NMR (125 MHz) were run on a DRX-500 (Brüker) spectrometer using solvent resonances to calibrate the spectra.
Plant material
The material used and vouchers have been described previously (Midiwo et al., 1997).
Extraction
Extraction with ethyl acetate was done as previously described (Midiwo et. al., 1997) to give 494 g of exudate from aerial parts which when dried
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Major flavonoids from Psiadia punctulata produce vasodilation via activation of endothelial dependent NO signaling
2020, Journal of Advanced ResearchCitation Excerpt :The plant is characterized by the presence of different classes of phytochemicals, including diterpenes, flavonoids, and phenylpropanoids [8–10]. PP has traditionally been used to treat cold, abdominal pain, fever, malaria, scabies and skin infection; as analgesic and expectorant; and to remove ectoparasite from cattle [8,9]. Other studies have reported PP leaves to exhibit antifungal and pesticide activities [11], while its bark showed antiprotozoal activity against Leishmania major [12].
Phytochemistry of compounds isolated from the leaf-surface extract of Psiadia punctulata (DC.) Vatke growing in Saudi Arabia
2018, PhytochemistryCitation Excerpt :Only one flavonoid (i.e. gardenin C, 28) among those isolated from P. Punctulata was previously reported from a Saudi Arabian accession of this species (Abou-Zaid et al., 1991). Psiadiarabin (Al-Yahya et al., 1987), 5,3′-dihydroxy-7,2′,4′,5′-tetramethoxyflavone, 5-hydroxy-7,2′,3′,4′,5′-pentamethoxyflavone (El-Feraly et al., 1990), and 5,7,3′-trihydroxy-2′,4′,5′-trimethoxyflavone (Mossa et al., 1992), attributed to P. arabica, as well as cirsilineol, gardenin B, 5-hydroxy-3,6,7,4′-tetramethoxyflavone, 5,3′-dihydroxy-6,7,4′,5′-tetramethoxyflavone, 5-hihydroxy-6,7,3′,4′,5′-pentamethoxyflavone (Abou-Zaid et al., 1991), 5,7-dihydroxy-2′,3′,4′,5′-tetramethoxyflavone, 5,4′-dihydroxy-7,2′,3′,5′-tetramethoxyflavone, and 5,7,4′-trihydroxy-2′,3′,5′-trimethoxyflavone (Juma et al., 2001), attributed to P. punctulata, were not found in the accession studied. ent-Kaur-16(17)-en-6,18,19-triol-2-one (16) (El-Domiaty et al., 1993), ent-kaur-16(17)-en-2α,18,19-triol (17) (El-Shafae and Ibrahim, 2003; Midiwo et al., 1997), ent-Trachyloban-18,19-dihydroxy-2-one (18) (Midiwo et al., 1997), ent-trachyloban-2β,6β,19-triol (19) (Midiwo et al., 1997), ent-trachyloban-6β,18,19-triol (20) (Juma et al., 2006) and ent-trachyloban-2α,17,18-triol (21) (Juma et al., 2006) have been previously attributed to African plants of P. punctulata.
The genus Psiadia: Review of traditional uses, phytochemistry and pharmacology
2018, Journal of EthnopharmacologyCitation Excerpt :Chromatographic separation of an aqueous ethanolic extract of the leaves of P. punctulata afforded 16 flavonoids: apigenin (27), acacetin (28), chrysoeriol (29), luteolin (30), luteolin-7-O-glycoside (31), orientin (32), orientin-7-O-glucoside (33), isoorientin (34), isoorientin-7-O-glucoside (35), cirsilineol (36), gardenin B (37), 5-hydroxy-3,6,7,4′-tetramethoxyflavone (4), 5,3′-dihydroxy-6,7,4′,5′-tetramethoxyflavone (39), 5-hydroxy-6,7,3′,4′,5′-pentamethoxyflavone (40) and gardenin C (38) (Abou-Zaid et al., 1991). From the leaf exudate, three new flavonoids were purified in addition to compounds (7) and (25) that had been previously described (Juma et al., 2001). These three molecules were isolated by silica gel chromatography: 5,7-dihydroxy-2′,3′,4′,5′-tetramethoxyflavone (22), 5,4′-dihydroxy-7,2′,3′,5′-tetramethoxyflavone (23) and 5,7,4′-trihydroxy-2′,3′,5′-trimethoxyflavone (24).
Three ent-trachylobane diterpenes from the leaf exudates of Psiadia punctulata
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