**4. Bioactive compounds from diverse plant, microbial, and marine sources**

Plant-based bioactive compounds, which are called phytochemicals, are the secondary metabolites of the plant that normally are produced to protect the plant against insects and animals. In the human body, however, they can prevent and reduce the risk of some types of cancer or chronic diseases such as diabetes. Phytochemicals' favorable properties have brought researchers' interest towards them and resulted in isolating and identifying thousands of plant-based bioactive compounds. Vitamin C, folate, provitamin A, potassium, calcium, magnesium, flavonoids, phenolics acids, alkaloids, carotenoids, and fibers are among the outstanding ones that could be mentioned [24]. Here, some of the plants that are sources of phytochemicals are mentioned. The *Origanum Spp*. has different terpene derivatives and phenolic compounds. These compounds exist in the essential oil extracted from the plant and have shown antibacterial, antioxidant, and anti-inflammatory activities. The *Thymus spp*., especially the flowers are rich in terpenes, terpene alcohols, phenolic derivatives, ketones, aldehydes, ethers, and esters. Although the chemical composition highly depends on the species. *Salvia Spp.* has terpenic, flavonoid, phenolic acid, and steroid structures and therefore can be utilized to extract anti-microbial and anti-oxidant phytoconstituents [25].

There are various microbes such as bacteria, fungi, and cyanobacteria that produce bioactive compounds through their metabolic pathways [26].

Cyanobacteria are microorganisms with characteristics similar to bacteria and fungi, they have 2000 species and are a great bioresource of pigments. During screening programs in search of bioactive compounds, cyanobacterial metabolites are with potential use in fluorescent probes have been found. Cyanobacteria consist of phycobiliproteins, molecules valuable as sensing elements in biosensors for light characterization [27].

Probiotics are a vast source of beneficial bioactive materials, among them *Lactobacillus spp., Bifidobacterium spp., Clostridium spp*., and, Enterobacteriaceae are known for producing metabolites with health benefits such as amino acids, vitamins, and folates [28].

There are two major groups of marine algae: (A) Microalgae that is divided into 4 types *Chlorophyta* (green algae); *Chrysophyta* (golden-brown, yellow algae, and diatoms); *Pyrrhophyta* (dinoflagellates); *Euglenophyta.* They produce a type of toxin called dinoflagellate and could be used in studying cellular processes. (B) Macroalgae that consists of seaweeds and marine vegetables, they are a resource for hydrocolloids and phycocolloids, these two are being used as gelling substances, emulsifying agents, and wound dressing [29].
