In this study, extraction of essential oil, polyphenols and pectin from orange peel has been optimized using microwave and ultrasound technology without adding any solvent but only "in situ" water which was recycled and used as solvent. The essential oil extraction performed by Microwave Hydrodiffusion and Gravity (MHG) was optimized and compared to steam distillation extraction (SD). No significant changes in yield were noticed: 4.22 ± 0.03% and 4.16 ± 0.05% for MHG and SD, respectively. After extraction of essential oil, residual water of plant obtained after MHG extraction was used as solvent for polyphenols and pectin extraction from MHG residues. Polyphenols extraction was performed by ultrasound-assisted extraction (UAE) and conventional extraction (CE). Response surface methodology (RSM) using central composite designs (CCD) approach was launched to investigate the influence of process variables on the ultrasound-assisted extraction (UAE). The statistical analysis revealed that the optimized conditions of ultrasound power and temperature were 0.956 W/cm(2) and 59.83°C giving a polyphenol yield of 50.02 mgGA/100 g dm. Compared with the conventional extraction (CE), the UAE gave an increase of 30% in TPC yield. Pectin was extracted by conventional and microwave assisted extraction. This technique gives a maximal yield of 24.2% for microwave power of 500 W in only 3 min whereas conventional extraction gives 18.32% in 120 min. Combination of microwave, ultrasound and the recycled "in situ" water of citrus peels allow us to obtain high added values compounds in shorter time and managed to make a closed loop using only natural resources provided by the plant which makes the whole process intensified in term of time and energy saving, cleanliness and reduced waste water.

Vegetal extracts are widely used as primary ingredients for various products from creams to perfumes in the pharmaceutical, nutraceutic and cosmetic industries. Having concentrated and active extract is essential, as the process must extract as much soluble material as possible in a minimum time, using the least possible volume of solvent. The boldo leaves extract is of great interest for the industry as it holds a great anti-oxidant activity due to high levels of flavonoids and alkaloids such as boldine. Ultrasound Assisted Extraction (UAE) has been used to improve the efficiency of the plant extraction, reducing extraction time, increasing the concentration of the extract with the same amount of solvent and plant material. After a preliminary study, a response surface method has been used to optimize the extraction of soluble material from the plant. The results provided by the statistical analysis revealed that the optimized conditions were: sonication power 23 W/cm2 for 40 min and a temperature of 36 °C. The optimized parameters of the UAE provide a better extraction compared to a conventional maceration in terms of process time (30 min instead of 120 min), higher yield, more energy saving, cleanliness, safety and product quality.

Microwave extraction and separation has been used to increase the concentration of the extract compared to the conventional method with the same solid/liquid ratio, reducing extraction time and separate at the same time Volatile Organic Compounds (VOC) from non-Volatile Organic Compounds (NVOC) of boldo leaves. As preliminary study, a response surface method has been used to optimize the extraction of soluble material and the separation of VOC from the plant in laboratory scale. The results from the statistical analysis revealed that the optimized conditions were: microwave power 200 W, extraction time 56 min and solid liquid ratio of 7.5% of plants in water. Lab scale optimized microwave method is compared to conventional distillation, and requires a power/mass ratio of 0.4 W/g of water engaged. This power/mass ratio is kept in order to upscale from lab to pilot plant.

IntroductionWater is the most abundant molecule on the earth, covering 70% of its surface. Life processes on this planet are crucially dependent on the presence of water. It is often recognized that water has tremendous benefits as a green extraction solvent because it is not only inexpensive and environmentally benign but it is also nonflammable and nontoxic, providing opportunities for clean processing and pollution prevention. The water molecule contains three nuclei, one modestly heavy (oxygen), and two light ones (hydrogen). Because of water's electronic structure, the oxygen atom has a slight negative charge on it and the hydrogen atoms have a slightly positive charge [1]. When water molecules are closed together, their positive and negative regions are attracted, these attractive forces are known as hydrogen bonds. The energy associated with a hydrogen bond is 8-40 kJ/mol. The O-H bond lengths are 0.9572 Å and the average HOH bond angle is 104.52 ∘ , slightly smaller than the tetrahedral angle (109.5 ∘ ). The molecule is very small with a hard sphere diameter of 2.75 Å. The smallness of the water molecule has important consequences for the hydration of solutes. The contours of the total electron density in the HOH plane of the water molecule indicate a shape not far from spherical. The water molecule has a dipole moment of 1.85 D with two partial positive charges on the hydrogen atoms and a single zone of negative charge on the oxygen atom.It is well known that water molecules are strongly associated in the liquid phase by H-bonding. Hydrogen bonds result dominantly from electrostatic interactions with a light contribution of covalent bond formation. The H-bond interactions in liquid water constitute a 3-D H-bond network with localized and structured clustering. Therefore, the liquid structure is not determined by hard-core repulsions between the individual water molecules but rather by intermolecular and directional H-bonding. The broad variation of H-bond angles further demonstrates the noncrystalline arrangement of the water molecules and appears to indicate that some bond angle distortion in the H-bonds is rather easily allowed in the liquid. It is important to recognize that intermolecular interaction Green Extraction of Natural Products: Theory and Practice, First Edition. Edited by Farid Chemat and Jochen Strube.

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