ABSTRACT
Solenostemon monostachyus is an important herb that is native to West and Central Africa. The leaves have traditional use for the treatment of various ailments such as ulcer, hypertension, malaria, diabetes and inflammatory diseases. The isolation from the leaves of Solenostemon monostachyus plant gave the isolated compound kaempferol-3-o-β-glucoside which is a major flavonoid glucoside and has been reported to have analgesic, anti- inflammatory, anti- influenza virus, antioxidant and anti- diabetic activities. The analgesic activity, demonstrated that Solenostemon monostachyus plant (mostly the leaves) possesses analgesic property (peripheral and CNS) thus providing justification for the ethno-botanical studies of the use of the Solenostemon monostachyus in traditional practices of herbal medicine.
The dried leaves, flowers and stem of Solenostemon monostachyus were reduced to powdered form by mechanical grinder separately. Various plant parts were analyzed for moisture, protein, ash, fat, fibre and nitrogen free extract and also for iron, calcium, magnesium, zinc, manganese, potassium and sodium. One thousand grams (1000g) each of the pulverized leaves, flowers and stems were extracted by cold maceration with methanol for 72 hours. Phytochemical screening was performed on the methanol crude extracts of leaves, flowers and stem according to standard methods. Bioassay guided of the methanol crude extract of leaves, flowers and stem crude extracts was carried out using acetic acid induced and hot plate methods on the mice. Isolation was done using combination of chromatographic techniques while characterization of the compound was carried out with fourier transform infra- red spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV), gas chromatography- mass spectroscopy (GC-MS), 1H and 13C nuclear magnetic resonance (NMR). The acute toxicity and analgesic activity were done on Swiss mice according to standard methods.
The proximate composition of the leaves, flowers and stem revealed moisture content varied from 0.87- 1.67%. The ash content has a range of 9.70- 14.80%. The protein value falls within 3.94- 7.44%. Crude fat ranged from 18.67- 20.97%. The crude fibre falls within the values of 40- 25.60%. The carbohydrate content varied from 36.23- 52.53%. The mineral analysis of the leaves, flowers and stem revealed the presence of iron, calcium, magnesium, manganese, potassium and sodium. The bioassay guided confirmed that the methanol crude extract of the leaves was more effective compared to the flowers and stem for the treatment of peripherally mediated pain, therefore, the leaves extract was used for characterization of the compound. Spectroscopic data for isolate 4B-1 gave UV -Vis at 331.0nm and 535.0nm indicating a bathochromic shift from a shorter wavelength to a longer wavelength due to the presence of auxochrome. There were major I.R bands at 3408.08cm-1 (O-H Stretch), 2863.63cm-1 (C-H stretch), 1738.14cm-1(C=O stretch), 1658.20cm-1(C=C), 1598.49cm-1, 1451.99cm-1(Aromatic ring), 1049.22cm-1 (C-O-C) and 838.17cm-1 (Glycosidic linkage). The 1HNMR revealed the presence of four olefin methine proton signal at δH 7.90 (d) and δH 6.93 (d) due to para disubstituted benzene ring and two additional olefin methane proton signalsat δH 6.31 (d) and δH 6.14 (d) due to the presence of meta- aromatic protonindicating a kaempferol moiety. It also revealed the presence of an anomeric proton signalat δH 5.26 (d), four oxygenated methine proton signalsat δH 3.58 (t) and δH3.65 (m). and one methylene protonat δH 3.79 (m) indicating the presence of a sugar moiety identified as β- glucoside. The 13CNMR spectrum revealed 21 carbon signals which were classified by their chemical shifts.It indicated a conjugated ketone carbon signal at δc 178.2,six oxygenated olefin quartenary carbon at δc166.4, δc 161.8, δc157.7, δc158.8, δc 156.4 and δc 135.1, two olefin quartenary carbon signal at δc 122.9, δc104.5 and six olefin methane carbon signals at δc 129.2, δc 115.8, δc 98.3and δc 94.0 were observed and this accounted for fifteen (15) carbon indicating the presence of kaempferol moiety.It also revealed anomeric carbon signal at δc 109.6, four oxygenated methine carbon signal at δc 75.1, δc 76.9, δc 71.5, δc 81.6 and one methylene carbon signal at δc 62.2 indicating a β- glucoside. From the FTIR, UV-Vis, 1H-NMR and 13C-NMR the data corresponds to molecular formula C21H20O11. Thus, the structure of compound 4B-1 was established as kaempferol-3-o-β-glucoside. The IUPAC name is 5,7-dihydroxy-2-(4-hydroxyphenyl)-3- [(2S,3S,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl) oxan-2-yl] oxychromen-4-one.
