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BACKGROUND Microalgae are one of the most promising biofuel sources that the world has to offer; nevertheless the conversion process is hampered by technical and economic problems that are mainly related to de-watering and extraction. The efficiency of the process can be dramatically improved by means of non-conventional techniques such as ultrasound ( US) and microwaves ( MW). Scaling-up feasibility is strictly linked to reactor efficiency, energy consumption, environmental impact and overall cost. In the present work, the optimization of lipid extraction from Nannochloropsis gaditana microalga is investigated. RESULTS A series of selected solvent mixtures and procedures have been tested and compared. Conventional extraction procedures with chloroform/methanol mixtures and fast US- and MW-assisted extractions with methanol gave comparable fatty acid ( FA) w/w% from dried microalgae. The highest extraction yield and lowest energy consumption was found to occur under MW irradiation, especially at high temperatures and under pressure. CONCLUSION This study highlights the advantages of US- and MW-assisted lipid extraction from microalgae, both in terms of efficiency and operational costs. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Polyphenols, the well known naturally occurring antioxidants, are the most abundant secondary metabolites in grape wastes. Herein we investigate several non-conventional extraction methods vs classic solid–liquid extraction (SLE) to obtain phenolic compounds from grape seeds and skins. We compared SLE, ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and high pressure and temperature extraction (HPTE) in term of extraction yield and antioxidant power of the extract. Solvent of choice between methanol and ethanol was the former, both for skins and seeds. Quali-quantitative analyses were performed using colorimetric and HPLC methods. The highest content in total polyphenols, o-diphenols and flavonoids, both for seeds (108.3, 47.0mgGAE gDW −1, 47.2mgCE gDW −1) and skins (34.2, 10.1mgGAE gDW −1, 21.6mgCE gDW −1) was obtained with HPTE working in a Parr reactor. While the highest antiradical power was determined in seeds extracts from MAE (78.6μlextract μgDPPH −1). Prolonged extraction times (over 30min) further increased the amount of total polyphenols, while progressively decreased the amount of flavonoids and the antiradical power. [Copyright &y& Elsevier]

Abstract: Mitragyna speciosa, a tropical plant indigenous to Southeast Asia, is well known for its psychoactive properties. Its leaves are traditionally chewed by Thai and Malaysian farmers and manual labourers as it causes a numbing, stimulating effect. The present study aims to evaluate alkaloid yield and composition in the leaf extracts. For this purpose we have compared several non-conventional extraction techniques with classic procedures (room temperature or under heating). Dried M. speciosa leaves belonging to three batches of different origin (from Thailand, Malaysia and Indonesia) were extracted using ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and supercritical carbon dioxide extraction SFE-CO2, using methanol, ethanol, water and binary mixtures. The extracts were compared using an HPLC/ESI-MS analysis of mitragynine and four other related alkaloids which were present in the alkaloid fraction. The extraction technique influences both the raw product yield and the relative alkaloid content of M. speciosa leaves. Of the several methods tested, MAE in a closed vessel at 110°C (60W, methanol/water 1:1) gave the highest alkaloid fraction amount, while UAE with an immersion horn at 25°C (21.4kHz, 50W, methanol) showed the best yield for mitragynine. This work may prove to be a useful contribution to forensic, toxicological and pharmacognosy studies. Although the potential applications of M. speciosa alkaloids clearly need further investigation, these results may facilitate the scaling-up of their extraction. [Copyright &y& Elsevier]