This review appraises the chemical conversion processes recently reported for the production of hydroxylmethylfurfural (HMF), a key biorefining intermediate, from carbohydrate biomass feedstocks. Catalytic sites or groups required for the efficient and selective conversion of hexose substrates to HMF are examined. The principle of concerted catalysis was used to rationalise the dehydration of fructose and glucose to HMF in non-aqueous media. A survey of reported reaction routes to diesel-range biofuel intermediates from HMF or furfural is presented and self-condensation reaction routes for linking two or more HMF and furfural units together toward obtaining kerosene and diesel-range biofuel intermediates are highlighted. The reaction routes include: benzoin condensation, condensation of furfuryl alcohols, hetero Diels-Alder reaction and ketonisation reaction. These reaction routes are yet to be exploited despite their potential for obtaining kerosene and diesel-range biofuel intermediates exclusively from furfural or hydroxylmethylfurfural.

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Citrus aurantifolia leaf essential oil was extracted via hydrodistillation, chemical composition of the oil was analyzed using gas chromatography-mass spectrometry and its antidiabetic potentials was assessed in alloxan-induced hyperglycaemic rats using metformin as the reference drug for comparison. Chemical analysis showed that D-limonene (57.84%) was the major constituent of the oil. Other notable compounds identified were neral (7.81%), linalool (4.75%), sulcatone (3.48%) and isogeraniol (3.48%). Intraperitoneal administration of C. aurantifolia oil (100 mg/Kg b.wt.) to hyperglycaemic rats for 14 days caused significant reduction in fasting blood and hepatic glucose, whereas hepatic concentration of glycogen was significantly increased. Also, improvement in dyslipidaemia was observed in C. aurantifolia essential oil-treated hyperglycaemic rats; serum concentration of total cholesterol, triacylglycerol and low density lipoprotein-cholesterol were significantly reduced and high density lipoprotein-cholesterol was increased, resulting in decreased predisposition of rats to cardiac risks. Antihyperglycaemic potential of administration of the oil was lower but compared favourably with the oral antihyperglycaemic agent used as reference antidiabetic drug. Overall, data from this study showed that essential oil from the leaf of C. aurantifolia grown in North-Central Nigeria is a D-limonene chemotype. The oil showed considerable glucose lowering effect as well as the potential to ameliorate hyperglycaemia-induced dyslipidaemic complications in alloxanized rats.

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The insecticidal properties of Hoslundia opposita Vahl (Lamiaceae) leaves' essential oil (EO) against Tribolium castaneum were investigated using contact toxicity and repellency bioassays. Mortality progressed with exposure period and ranged from 61.13% observed at 24 h after treatment (HAT) to 88.86% at 168 HAT. The LT50 (lethal time for 50% of treated adults) of H. opposita EO against T. castaneum was 10.42 h. Application of EO at 20-30 μL/30 cm(2) caused significantly (P < 0.05) higher percentage repellency than what was observed in control, 10 and 15 μL/30 cm(2) at 1 and 3 HAT, with significant repellency at 24 HAT regardless of dosage. Repellency class increased with EO dosage, with class V observed at 30 μL/30 cm(2), regardless of exposure duration. The RD50 (repellency dose for 50% of treated adults) of 15.88 and 13.37 μL/30 cm(2) for 1 and 2 HAT, respectively, was significantly higher than 0.09 μL/30 cm(2) at 24 HAT.

SUMMARY Dependence on fossil fuels for global energy supply has continued to generate concerns about climate change and sustainable development. It has motivated the search for carbon‐neutral alternative resources for the production of transportation fuels to replace crude oil. Although biodiesels have recently emerged as a close substitute to petrol diesel, their use in compression ignition engines designed to run on petro‐diesel fuels are linked to adverse effects on the engines' performance and life span. This informed efforts at upgrading biodiesel or direct conversion of triglycerides to hydrocarbon mixtures that are identical or similar to that of petro‐diesel through hydrodeoxygenation. Moreover, it seems that commercial methods for the conversion of triglycerides to diesel fuels depends on inputs (methanol and hydrogen) derived from fossil fuels. However, it will be desirable to do so without inputs from fossil fuels. Hence, reaction paths for direct conversion of triglycerides to on‐specification hydrocarbons fuels without hydrogen gas input are discussed and suggested strategies are in cognisance of green chemistry principles. Copyright © 2012 John Wiley & Sons, Ltd.

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