Citrus Peels as a Source of Bioactive Compounds with Industrial and Therapeutic Applications

*Doha Hussien Abou Baker, Eman Ahmed Ibrahim and Zeinab Abd El-Rhaman Salama*

### **Abstract**

Agriculture wastes are considered a good starting point to discover for new drugs all over the world. In this context, Agriculture wastes contain millions of compounds to be screened to find bioactive compounds responsible for the activity to be used in drugs. Citrus agriculture is one of the most important commercial and industrial agricultural activities in the world. The peel waste of Citrus species is a rich source of bioactive compounds such as essential oils, flavones, polyphenols, and pigment. Citrus peel has been widely used in the medicine industry. The waste peel of citrus consider a rich source of pharmacologically active metabolites with antioxidant activities.

**Keywords:** Citrus waste, Phenolic compounds, Liminoids, Antioxidant activity, Therapeutic Activity, Industrial uses

### **1. Introduction**

Agriculture crops, fruits, vegetables, cereals, bean crops produce large amount of wastes or by-products. These huge amounts of wastes could be of significant value if properly utilized. They could be more valuable than the main products and hence an added value will maximize these wastes. The main uses of these wastes are as animal feed or as compost used in enhancing soil fertility and used instead of chemical fertilization. Some products wastes such as banana stem waste can be used as an fiber for hand made paper and several grades of recycled papers. Beet waste can produce natural colors. Papaya is used as medicine (papain), toothpaste and meat tenderizers. Pine apple core for natural sweetener, grape pomace is a source of tartaric acid and polyphenols a natural antioxidants. Resveratrol a compound found in grape pomace known for its beneficial cardiovascular effects. Citrus peel includes cellulose, hemicellulose, lignin, pectin (galacturonic acid), chlorophyll pigments and other low molecular weight compounds (eg limonene) [1]. Polyphenol from grape seeds is used for management of Alzheimer disease [2]. Imitation vanilla is a liquid concentrate comes from treated wood pulp by –products.

In Egypt the major cultivated fruit trees are citrus, which came after mango and grapes in its cultivated area. Citrus has been cultivated in Egypt since ancient times, and there are some types grown in different regions such as Baladi orange, sweet (sugar) orange, and blood orange mandarin, lime, lemon, grapefruit, sour orange, kumquat, shadouk, pummelo and citron. At present, the area of citrus cultivation has increased rapidly, as this area reached 204,095 hectares, representing about 29% of the total fruit area (700,854 hectares), while the total productive area reached about 175734 hectares, producing approximately 4.27 million metric tons [3]. In Egypt these wastes were a main sources of agricultural cultural waste. The main use of these wastes are as animal feed or as compost. However higher amounts of these wastes were burned in the field or throwed in water canals, causing hazards and environmental pollution [4]. Recycling of such residues is one suitable technology adopted in industrial and developed countries, because these wastes are high value product and their recovery may be economically attractive. Citrus juice production generates 15 million tons of waste annually in the world, including peels, seeds, and fruit pulp [5].

Recently there is increase in the use of plant byproducts. The availability, potentiality, no side effect and no cost of byproducts in comparison to modern therapeutic drugs for the treatment of dangerous diseases such as cancer, and Alzheimer makes them more attractive [2, 6, 7]. Citrus fruits are the biggest fruit sector production all over the world, at the same context, waste the dominant byproduct of Citrus processing industries [8]. These citrus fruit residues, which are generally discarded as waste in the environment, can act as potential nutraceutical resources. Due to their low cost and easy availability such wastes are capable of offering significant low-cost nutritional dietary supplements. The utilization of these bioactive rich citrus residues can provide an efficient, inexpensive, and environment friendly platform for the production of novel nutraceuticals or for the improvement of older ones.

Citrus by –products is a major source of phenolic compounds; flavonoids, [9]. These flavonoids belong to six classes and have different biological activities i.e. antioxidant, anticancer, antiviral and antinflammatory. Dimou et al. 2019 on their review concluded that by –product of fruits and vegetables have an important role to be used as functional activity in cosmotics, nutraceuticals and as functional foods either in their raw material for additive processes or as ingredients for a new products [10]. Citrus waste have limonoids and flavonoids as their anticancer constituents. The most abundant citrus flavonoids, generally known as the flavanones, include hesperidin, naringin, narirutin, and neohesperidin, and these compounds have been found to provide health benefits such as antioxidative, anticancer, antiinflammatory, and cardiovascular protective activities. Furthermore, the consumption of naringin and hesperidin reduced cholesterol levels in hamsters by 32 to 40% [11].

### **2. Materials and methods**

The peel waste of citrus fruit after juice extraction was obtained from a local food processing company. Samples were extracted using a different polar solvent. Yield extract of peels by different solvent was determined phenol contents according to Singleton et al., [12] total flavonoid were assayed by method Zhishen et al. [13].

Extract Limonin from citrus pee were prepared and purified according to the procedures Tian et al., and Tian et al. [14, 15]. A kilogram of powder peels was extracted (Soxhlet) overnight with hexane at 25°C to remove the oil. The solvent was changed to acetone and methanol sequentially to extract the peels. The methanol fraction was evaporated by a rotary evaporator under vacuum at 60°C and the residue was partitioned with 1:1 methylene chloride-water using an ultrasonic sonicator. The

*Citrus Peels as a Source of Bioactive Compounds with Industrial and Therapeutic Applications DOI: http://dx.doi.org/10.5772/intechopen.99591*

methylene chloride fraction and the previous acetone fraction were combined and evaporated to dryness or purification of the limonoid aglycones. Limonin was purified by repeated crystallization in methylene chloride and isopropanol.

Extraction of the essential oils.a kilogram of citrus peel were macerated in 1Lof distilled water during 24 h before extraction. Peels were then submitted to Clevenger hydrodistillation for 3 h. The obtained the essential oils were dried over anhydrous sodium sulfate and after filtration stored at 4C. The yield of extraction was isolated according to Williams and Lasunzi [16].
