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This article reviews the excited-state quenching, pro-vitamin A activity and anticarcinogenicity of carotenes and xanthophylls in relation to their chemical structures. Excited-state quenching improved with the length of the conjugated chain structure. Pro-vitamin A activity was dependent on the presence of at least one beta-ionyl ring structure. The effectiveness of carotenoids as antioxidants depended on their ability to trap peroxyl radicals with production of resonance-stabilized carotenyl radicals. The products identified from oxidations of carotenes and xanthophylls with molecular oxygen and other oxidizing agents are presented. The free radical-mediated mechanisms that have been proposed to account for the different classes of products are reviewed.

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The phytochemical constituents, antimicrobial activity, anti-mycobacterial activity and gas chromatography-mass spectrometry (GC-MS) analysis of the West African ecotype of Bidens pilosa was investigated for possible medicinal properties. The antimicrobial activity of the hexane, dichloromethane, ethyl acetate and methanol extracts from the leaf of Bidens pilosa was evaluated using agar dilution method. The qualitative and quantitative phytochemical screening was carried out according to standard procedures. Partitioned fractions of the methanolic extract was subjected to anti-mycobacterial bioassay. Different fractions of the leaf were subjected to GC-MS to ascertain the compounds present. The antimicrobial analysis revealed the methanolic fraction as having the highest number of activity against test organisms such as: Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Candida albicans and Rhizopus sp. between 10 – 40 mm. The minimum inhibitory concentration showed the methanolic fraction to be active against Candida albicans and Rhizopus sp. at the concentration of 6.25 g/ml and 3.25 g/ml respectively. The phytochemical screening revealed the presence of alkaloids, cardiac glycosides and terpenoids in all the solvents. Tannin was present in all the solvent fractions except hexane fraction. Saponin was not found in any of the solvents. The hexane-methanol interface of the partitioned solvents was sensitive to the anti-mycobacterial activity while other solvents showed resistance. The GC-MS and the chromatogram gave insight into the volatile components of the leaf extract. The findings reveals Bidens pilosa as a medicinal plant with potentials for the treatment of tuberculosis.

Surpassing heart diseases, cancer is taking the lead as the deadliest disease because of its fast rate of spreading in all parts of the world. Tireless commitment to searching for novel therapeutic medicines is a worthwhile adventure in synthetic chemistry because of the drug resistance predicament and regular outbreak of new diseases due to abnormal cell growth and proliferation. Medicinal chemistry researchers and pharmacists have unveiled quinoxaline templates as precursors of importance and valuable intermediates in drug discovery because they have been established to possess diverse pharmacological potentials. Hence, this review highlights the current versatile routes to accessing functionalized quinoxaline motifs and harnessing their documented therapeutic potentials for anticancer drug development.