Further Pharmacognostical and Biological Studies on the Flowers of Oenothera Speciosa Nutt. Cultivated in Egypt

The effect of the time of collection on the phenolic content of the flowers of Oenothera speciosa Nutt., cultivated in Egypt, was studied. Samples collected at the early (March) and late (July) flowering periods were analyzed. Flavonoids (expressed as aglycones) and phenol acids were determined by HPLC in the hydrolyzed extracts. Samples gathered in March showed a relatively high percentage of flavonoids (407.05 mg/100g dry wt.) which decreased in the July sample, amounting only to 180.20 mg/100g dry wt. On the contrary, an increase was observed in the phenol acid content which reached 201.89 and 548.59 mg/100g dry wt. in the two samples, respectively; however, the qualitative pattern appeared the same for all constituents. In addition, gravimetric and spectrophotometric determinations of tannins and proanthocyanidins revealed that both were higher at the late flowering period (10.53 g% and 23.35g%, respectively) than at the early one (8.67g% and 19.03g%, respectively). Two flavonol glycosides; hyperoside (quercetin-3-O--β-D galactoside) and rutin (quercetin-3-O-α-L-rhamnose-β-D-glucoside) and the aglycone, quercetin, as well as a phenol acid, chlorogenic acid, were isolated via chromatographic fractionation of the ethyl acetate extract. (+) Catechin, isolated from the acetone extract, constituted the major component of the tannin fraction. Characterization of the isolated compounds was achieved through physical, chemical, chromatographic and spectral analyses, as well as, by comparison with available authentic samples. Moreover, the carbohydrate content was investigated by PC and HPLC. Rhamnose, arabinose and glucose were identified as free sugars. Analysis of the hydrolyzate of the cold extracted mucilage (CEM) revealed the presence of galacturonic, glucuronic acids and galactose in addition to the aforementioned sugars. Likewise, the hydrolyzate of the hot extracted mucilage (HEM) differed from that of (CEM) in containing xylose and appearing free from arabinose. The aqueous and alcoholic extracts, as well as, the hot extracted mucilage (HEM), were subjected to biological evaluation as compared to standard drugs. Their safety was ascertained through determination of their LD50. The alcoholic extract exhibited more potent antiinflammatory, analgesic, anti-oxidant and antiulcer activities as compared to the aqueous extract. Meanwhile, HEM exerted a more pronounced anti-hyperglycemic action than the alcoholic extract. The alcoholic extract, moreover, revealed noticeable antibacterial and antifungal activities, while those observed for the aqueous extract were only moderate. Finally, the macroand micromorphological characters of the flowers are described with the aim to provide useful data for identification and differentiation of the plant from other allied species either in the entire or powdered form.