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Natural products involved in plant-plant and plant-microorganism ecological interaction (Allelochemicals) are an important potential source for alternative agrochemicals and pharmaceuticals, in order to solve the many problems derived from inadequate culture practices and abuse of synthetic herbicides. Isolation, structural determination, bioassay techniques and applicability for these compounds in crop protection and pharmaceutical research are discussed, and future trends on Allelochemicals applications are examined. The new strategies for sustainable ecosystems controlled by allelochemicals offer a particular interest for the development of human bases in space, since these products can stimulate or inhibit plant germination and growth, and permit to develop crops with low residue amounts in water, facilitating wastewater treatment and recycling.

The development of new bioactive molecules with potential application in pharmacology and agriculture by using natural products as templates has been a widely used approach in the recent years. Focusing our attention in phytochemicals with potential application in agriculture, allelochemicals (natural plant toxins) have been deeply researched with the main purpose of finding phytotoxic substances to use as new herbicidal templates. The development of new analytical methodologies, improved bioassay techniques and a complete understanding of the allelopathic phenomenon will provide new tools for natural herbicide models development, in the context of the new approaches to integrated pest management. A deeper knowledge of the release and assimilation of allelochemicals, and the degradation phenomena associated to them will aid to discover new chemical structures with potential utility, in addition to a better understanding on the ecological interactions mediated by phytochemicals. The research on these topics, made with promising allelochemicals such as benzoxazinones and their degradation derivatives, the improvements on analytical design, the degradation mechanisms elucidation and the novel bioassay techniques recently developed, are revised herein.

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The onion is one of the most cultivated and consumed vegetables, and is a very valuable source of antioxidant substances. Every onion variety is rich in flavonols—mainly quercetin derivatives which makes onions the main dietary source of these compounds. This study intends to develop an ultrasound-assisted extraction method (UAE), an economical, green, and efficient technique, that allows us to determine the quality of onion extracts in terms of flavonol composition and antioxidant activity. For this purpose, an ultrasound-assisted extraction method has been optimized to obtain extracts with a high amount of flavonols, as well as with a high antioxidant activity, not only separately using a Box–Behnken design, but also simultaneously, based on multi-response optimization. Multiple response optimization has not only demonstrated an efficacy level similar to that of the individual ones, but it also represents a considerable reduction in terms of cost, time and work. The optimal conditions for simultaneous extractions were determined as follows: 76.8% methanol as an extraction solvent at pH 2 and 58.5 °C temperature, 85% amplitude, 0.9 s cycle, and 0.2:13 g:mL sample mass/solvent volume ratio. Furthermore, the developed method exhibited a high precision level and great recoveries in a rather short extraction time (2 min). These results, together with the development of a fast and simple UHPLC analysis method, lead us to consider the developed UAE method as a suitable technique for the extraction of bioactive compounds from onion matrices.

Chokeberry (Aronia melanocarpa L.) contains a large number of bioactive compounds, which make of it a highly nutritional and antioxidant food with anti-cancer and anti-inflammatory properties. It has been recently seen its consumption increased because of its interesting composition and properties as a functional food. The ultrasound-assisted extraction method has been optimized, since it is a simple and fast technique to extract phenolic compounds, as well as anthocyanins, not only separately but also simultaneously. Multiple response has been optimized and demonstrated an effectiveness level similar to the individual ones. This represents a considerable reduction in costs, time and work. The optimal conditions for simultaneous extractions were: 54% methanol as extraction solvent at pH 2.72 and 69.4 °C temperature, 70% amplitude, 0.7 s cycle, and 0.5:18.2 g:mL sample mass/solvent volume ratio. The developed methods showed a high precision level with coefficients of variation lower than 5%. The methods were successfully applied to commercial samples. Additionally, the extraction of other compounds of biological interest, such as organic acids and sugars, was also studied.