Phytochemical analysis and antioxidant evaluation of lemon grass (Cymbopogon citratus DC.) Stapf leaves

Cymbopogon citratus commonly called lemon grass is claimed to possess diverse medicinal value among different cultures. The present study determined the phytochemicals and evaluated the antioxidant potential of Cymbopogon citratus leaves. The phytochemical and proximate analysis of the powdered leaves were carried out using standard methods. The antioxidant activity of the crude methanol extract and its fractions (n-hexane, ethyl acetate and chloroform) was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays. The total phenolic and flavonoid contents were assessed using the Folin-Ciocalteu and aluminium chloride colorimetric methods, respectively. The phytochemical analysis revealed the presence of carbohydrates, reducing sugars, saponins, tannins, flavonoids and other phenolics compounds. The moisture, ash, fat, crude fibre, crude protein, water soluble ash and acid insoluble ash contents were 13.00%, 7.63%, 2.44%, 29.40%, 4.45%, 6.13% and 4.00%, respectively. Among the extract and fractions tested, the ethyl acetate fraction exhibited the highest antioxidant activity. The ethyl acetate fraction also had the highest phenolic and flavonoid contents. There was a strong relationship between the polyphenolic content and antioxidant activity of the extract and fractions with a coefficient of determination (r²) of 0.889 and 0.920 for total phenols and total flavonoids, respectively. The present study showed that the leaves of Cymbopogon citratus especially the ethyl acetate fraction possess good antioxidant activity and could serve as potentially source of natural antioxidants.Keywords: Medicinal plants, Lemon grass, Cymbopogon citratus, Phytochemicals, antioxidant

Spectrophotometric assay of artesunate using benzaldehydes with electron withdrawing substituents

Different analytical methods have been reported for the assay of artesunate. However, these methods require the use of sophisticated and expensive equipment and reagents which are not readily available in many developing countries like Nigeria. This study is aimed at developing a method that is accurate, simple and cost effective using readily available reagents for the assay of artesunate in pure form and in pharmaceutical formulations. The developed spectrophotometric assay method is based on the fact that reactive methylene centre of the acid decomposed product of artesunate readily donates a proton that reacts with benzaldehyde to form a chromogen. This study involves the use of two benzaldehydes with electron withdrawing substituents, 3-bromobenzaldehyde and 4-chlorobenzaldehyde. Both gave immediate yellow coloured products and the wavelength of maximum absorption for the product obtained using 3-bromobenzaldehyde was 452 nm, while it was 456 nm for the product obtained with 4-chlorobenzaldehyde. However, the dissolution of 3-bromobenzaldehyde was incomplete in the acidic medium. The result obtained with 4-chlorobenzaldehyde revealed that Beer’s law was obeyed at the range of 20-100 μg/ml artesunate concentration with a linear coefficient of 0.9996 and the molar absorptivity was 2.1261×103 mol-1 cm-1. The limits of detection and quantification were 1.3832 μg/ml and 4.6109 μg/ml, respectively. The method required water as diluent. The result obtained from recovery studies by standard addition method confirmed that there was no interference from pharmaceutical excipients. The developed method was used to assay five brands of artesunate tablets successfully. The results compared favourably well with those obtained using the method described in the International Pharmacopoeia.Keywords: Artesunate, Benzaldehydes, spectrophotometry, recovery studie

Colorimetric determination of zidovudine in bulk and tablet dosage forms using potassium dichromate

A colorimetric method involving the oxidation of zidovudine (ZDV) using potassium dichromate in sulphuric acid has been developed for the determination of ZDV in bulk and tablet dosage forms. The wavelength of maximum absorption (λmax) of the oxidation product was determined and concentrations of sulphuric acid, potassium dichromate and amount/duration of heat were optimized. Beers plot was constructed at the λmax and used in the recovery studies for pure drug sample. Two methods (acid and methanol extraction) were used to extract ZDV from tablet samples. The developed method was then used to determine the percentage content of the drug in the tablets. The method was validated using the International Council for Harmonization of Technical Requirement for registration of Pharmaceuticals for Human Use (ICH) guideline. The λmax of the oxidation product was found to be 602 nm. The optimized conditions were as follows: 0.083M (potassium dichromate), 12 M (sulphuric acid) and heating at 90ºC for 30 mins. The regression equation for the Beer’s plots is: A = 0.4313C + 0.0018 (R2=0.9995) for ZDV. The recovery of ZDV from standard solutions was 100.36%±0.36. Thus the developed method was accurate and precise. The percentage contents determined for different brands of ZDV tablets were 99.07%±0.83, 98.70%±0.76, 93.46%±0.72 for the three brands of ZDV. These values compared well with results obtained with use of another method of assay. These values are within the specifications of the British Pharmacopoeia (90-110%). The limits of detection and limits of quantification were 0.004 and 0.014 mg/ml respectively. The developed method is simple, accurate, and utilizes readily available chemicals and equipment, and is inexpensive. It could therefore be used for the routine determination of ZDV.Keywords: Zidovudine, Oxidation, Colorimetric, Absorbanc