**3. Hydrosol**

Essential oils are decanted from the condensed water used as steam to separate them from the plant material. This condensed water, called hydrosol, hydrolat, distillation wastewater, or floral water, is obtained in amounts at least 50 times larger than the decanted essential oil and contains polar and hydrophilic essential oil components. A comparative study of the compositions of 44 hydrosols and their essential oils showed that in almost half of the hydrosols, the major component was different from that of the oil. Due to solubility differences, the concentrations of these organic substances are much smaller in hydrosol than in essential oil [6]. Some substances found in the hydrosol may result from molecular rearrangements caused by heating during distillation. For example, linalool and α-terpineol were found at higher concentrations in hydrosol than in *Lavandula angustifolia* essential oil [7].

There is a growing recognition of hydrosols as essential oil coproducts with many applications. *Mentha pulegium* and *Mentha suaveolens* hydrosols have shown high

insecticidal effects against *Toxoptera aurantii*, a citrus pest [8]. A study on the control of the *Myzus persicae* aphid pest showed that the application of *Melissa officinalis* or *M. pulegium* hydrosols on eggplant leaves had an inhibitory effect, while the use of *Origanum marjorana* hydrosol caused 10–15% mortality after 24 h [9]. These and many more recent reports support the increased use of hydrosols in biological agriculture against mushrooms, mildew, and insects. The hydrosol from *Cuminum cyminum* seeds has caused decreased hatching of root-knot nematodes, a widely spread pest of many plantations [10].

Hydrosols are increasingly recognized as sources of natural ingredients for cosmetic, nutraceutical, and food applications. One important biological activity in this respect is antioxidant capacity. It was found that hydrosols from basil, sage, and rosemary wastes of packaged fresh aromatic plant production contained caffeic acid derivatives, glycosylated luteolin, and other flavonoids, whose presence was manifested in their strong antioxidant capacity, similar to that of pomegranate juice and higher than that of red wine and green tea [11]. Bactericidal activity is also important for certain applications. A study of the hydrosols of basil, cardamom, clove, cinnamon, and thyme showed that they produced inhibitory effects against *Salmonella typhi, Staphylococcus aureus*, and *Escherichia coli* [12].
