AZERBAIJAN CHEMICAL JOURNAL № 3 2024 AZERBAIJAN CHEMICAL JOURNAL № 3 2024 102 1841 (Online) - ISSN 2522 2531 (Print) - ISSN 0005 UDC 66:57 COMPARISON OF SEVERAL EXTRACTION METHODS OF BIOMATERIALS (BY WATER) FROM SIX CITRUS SPECIES PEELS K.Ramadan, S.Nader, L.Mokrani Botany Department, Faculty of Sciences, Damascus University, Damascus, Syrian Arab Republic khaled.ramadan@damascusuniversity.edu.sy Received 27.04.2023 Reviewed 06.10.2023 Accepted 28.12.2023 Citrus species have interest from many researchers for a long time, due to their wide distribution and the diversity in of their chemical composition. On the other hand, it is very important to study and to con- sistently improve extraction methods in order to increase their efficiency. Several extraction methods based on six citrus species peels have been studied by comparing total yields and concentrations of some bio-compounds (phenols, carbohydrates, proteins and pigments), as well as the antioxidant activity. Ex- traction methods significantly differed in their results, due to the differences in the mechanisms of ac- tion. Extraction by Reflux assisted method gave the highest yield, but it was not the best method in total phenolic content. Maceration method was better in total phenolic content, however Ultrasound method gave the highest value of carbohydrates content. Generally, Citrus species have a high content of phe- nols and carbohydrates, low proteins content and good polar pigments content. Regarding TLC profile, there is an increase in metabolites (number of spots) when assisted extraction methods were used, so ex- traction by assisted methods increases both quantity and quality of extraction yield. It was noted that water was a suitable solvent for phenols and carbohydrates extraction. Using agricultural waste such as citrus peels has many biological, environmental, industrial and so economical benefits. Keywords: extraction methods, citrus, peels, biomaterials. doi.org/10.32737/0005-2531-2024-3-102-113 Introduction Citrus is one of the most abundant crops in the world, the major citrus producing coun- tries are China, Brazil, the United States, Mexi- co, India and Spain. Annual global production is about 147 million tons in 2021 [1]. Citrus belongs to Rutaceae family, fruit peel constitutes nearly 50% of the fruit mass, it is considered as an agricultural waste and a source of many natural compounds such as: es- sential oils, phenols, carbohydrates, pigments, fibers and vitamins; so it is widely used in nutri- tion, medicine and economic fields [2]. Extraction is the separation of a material or a chemical group from other chemical groups or from a raw material (such as plant mass) [3]. Selecting the appropriate extraction method as well as the solvent (specifically its polarity) depends mainly on the type of plant, plant parts and the nature of target bioactive compounds, so traditional extraction methods must be optimized [4]. Each extraction method has its own advantages and disadvantages, thus the diversity in extraction methods is always beneficial, considering the different conditions of each laboratory. Extraction methods classification: (A) Classical or Conventional extraction methods: Distillation, Soxhlet, Maceration, In- fusion, Decoction, Percolation, Digestion and Adsorption; have all the advantages to be easy, but take a relatively long time and need relative high temperatures for heating. The lake in ex- ternal conditions control like lighting could af- fect their efficiency and their bioactive material yield [5, 6]. (B) Modern or non-conventional methods (green extraction or green techniques): Ultra- sound assisted extraction, Microwave assisted extraction, Pressurized-liquid extraction, Super- critical fluid extraction, Enzyme assisted extrac- tion and Pulse electric field extraction. Modern methods are able to reduce solvents consump- tion, save time and avoid high temperatures,