Aloe plants, distributed in Old World, are generally known and have been used for ages as topical and oral therapeutic agents due to their beauty, health, medicinal, and skin care properties. Today, they account among the most valuable medicinal plants and are usually used in primary health treatment, where they act a pivotal role in the treatment of multiple types of diseases.
The nutrients and phytochemicals that have been recognized in Aloe plants include vitamins like (vitamin C, vitamin B1, vitamin B2 (riboflavin), vitamin B6, vitamin B12, and vitamin E), minerals like (calcium, magnesium, zinc, potassium, sodium, copper, iron, phosphorous, manganese, and molybdenum), enzymes, simple and complex polysaccharides, fatty acids, ketones, indoles, alkanes, pyrimidines, aldehydes, dicarboxylic acids, phenolic compounds and more.
Its name originates from the Arabic word “Alloeh”, symbolizing “shining bitter substance”.
Indeed, Aloe plants have been reported for various biological properties, including antibacterial and antimicrobial, anti-inflammatory, anti-arthritic, anti-rheumatoid, antitumor, anticancer, and antidiabetic activities, treating constipation, flushing out toxins and wastes from the body, detoxification, promoting digestion (on gastrointestinal disorders treatment), and decreasing illnesses likelihood, as well as for immune system deficiencies.
Traditional Medicine Use of Aloe Plants
Gastrointestinal activities, hepatoprotective properties, and beneficial effects against skin issues, such as wounds, injuries, and infective diseases, are among the most commonly reported Aloe species properties.
The most usually used part is leaf gel, which is effective for treating cuts and burns, gastrointestinal diseases such as indigestion, candidiasis, constipation, diarrhea, colitis, and digestive issue relief, such as heartburn and irritable bowel syndrome, and controlling blood pressure. 
A. vera uses include decreasing cholesterol in the blood; for miscarriage and anti-abortive therapy; treating arthritis, joint pains, body pains, and muscle pain; improving potentiality and sperm count; treating heart illness, depression, stress release, stability management, anger management, and so on. 
Jonson et al.  studied the antibacterial activity of leaf extract from Aloe vera, Pongamia pinnata, Lantona camara, Datura stromonium, and Calotropis procera. They discovered that from all of the tested alcoholic and aqueous extracts, A. vera displayed the strongest activity against S. aureus and E. coli.
A. vera sap and leaf extracts were examined for antimicrobial properties by Abakar et al. . They concluded that the juice got from aloe can be used for antimicrobial activity in cosmetics, pharmacy, and the food industry.
A. vera shows power antifungal activity against Candida species, specifically C. krusei, C. paraprilosis, and C. albicans.
Wound Healing and Cell Proliferation
In many types of research, procedure with whole A. vera gel extracts resulted in quicker wounds healing [175,176]. The mannose six-phosphate present in A. vera gel is recognized to be the active ingredient for wound healing .
Acemannan is considered to be a primary functional component of A. vera; Indeed, acemannan stimulates hard tissue regeneration and wound healing by inducing cell proliferation .
In traditional medicine, A. ferox leaves and roots are used topically, sometimes combined with animal fat, or taken internally to heal eczema, dermatitis, and acne. They are also applied in the treatment of various other skin disorders or conditions, such as skin burns, skin cancer, and psoriasis . The results verified that Aloe cream can be used to manage second-degree burn wounds, too .
Intestinal Absorption and Purgative Action
Anthraquinones that exist in plants act as strong laxatives through mucous secretion stimulation, also it increases intestinal water content . Active anthraquinones, such as aloe-emodin, aloin, and emodin are linked to aloe purgative effect [5,190]. Aloin, which is present mostly in gel, can be metabolized by colonic flora to re-active aloe-emodin, which is responsible for purgative activity [5,133].
Anti-Inflammatory and Immunomodulatory Effects
A. vera gel was also found to possess anti-inflammatory properties . The anthraquinones and chromones that are already in aloe inner gel have strong anti-inflammatory effects in murine macrophages .
A report of a clinical research has shown that the oral administration of 2% A. vera gel is not only useful in decreasing pain score and wound size in recurrent aphthous stomatitis patients, but also in lowering the aphthous wound-healing period .
In the literature, Aloe vera compounds were highlighted for their antioxidant properties [37,279,280]. It has been published that Aloe vera leaf epidermis and flower methanol extracts exerted in vitro antioxidant effects .
Antibacterial, Antifungal, and Antiviral Activities
Antibacterial activity has been assigned to their polysaccharides, which trigger phagocytic leucocytes to kill bacteria . Certainly, A. vera gel extracts antibacterial activity versus Gram-positive, and Gram-negative bacteria was confirmed in other studies [136,219].
The treatment of diabetes using numerous natural active compounds is still today high-priority research. In vivo and in vitro studies strongly proved that the water-soluble fraction of Aloe species has glucose-lowering activities.
An investigation confirmed that A. vera decreased diabetes severity by lowering blood glucose levels in type 2 diabetic patients . Other clinical studies have suggested that A. vera gel may act as a safe antihyperglycemic and antihypercholesterolemic agent in type 2 diabetic patients, without any significant effects on other normal blood lipid levels or liver/kidney function .
In a randomized controlled trial, A. vera gel complex reduced body weight, body fat mass, and insulin resistance in obese pre-diabetic and early non-treated diabetic patients .
A. vera antihyperlipidemic activity has also been reported. It had beneficial effects on fatty streak development prevention, and may help in reducing atherosclerosis development through risk factor modification . A. vera leaf gel efficacy was checked in hyperlipidemic type 2 diabetic patients in a randomized double-blind placebo-controlled clinical trial, wherein it reduced total cholesterol and low-density lipoprotein (LDL) levels .
Effect on Estrogen Status
Emodin and aloe-emodin segregated from Aloe vera gel suppressed breast cancer cell proliferation by targeting estrogen receptor-α protein stability throughout distinct mechanisms .
A. vera gel has the capability to minimize gastric ulcers in both animals and humans [30,267]. A. vera leaf extracts have also been generally recommended for digestion improvement and in peptic ulcer treatment due to its prominent cytoprotective effect, whereby A. vera gel exhibited antibacterial action against both susceptible and resistant H. pylori strains and served as a promising effective natural agent in combo with antibiotics on H. pylori gastric infection treatment [5,266].
Treatment of Cardiovascular Disorders
A. vera can be used for cardiovascular diseases treatment. It stimulated fibroblast cells for creating new tissues. Proteoglycans and collagens are created, thus reducing cardiovascular disorders risk, after fibroblasts stimulation .
Collagen, elastin, and hyaluronic acid are the crucial components of the skin dermis layer. Collagen creates the three-dimensional structure of the skin, and elastin keeps its elasticity, whereas hyaluronic acid improvements skin moisture levels. Fibroblasts are essentially responsible for collagen activation, and elastin in the skin dermis layer, hyaluronic acid, and thereby keep extracellular matrix homeostasis [270,271,272].
Treatment of Acquired Immune Deficiency Syndrome (AIDS)
It has been shown that acquired immune deficiency syndrome (AIDS) can be treated by using A. veraextracts in many reports. A daily intake of a minimum dose of 1200 mg of A. vera active ingredients improved AIDS symptoms. It soothed the wound and burn of internal organs, and hence acted as a promising AIDS drug. The mannose-6-phosphate present in A. vera can also inhibit the HIV-1 virus that causes AIDS .
Effect on Dental and Oral Diseases
It has been shown that acemannan hydrogels heal aphthous ulcers and reduce pain . A. vera is very effective for gum diseases, such as gingivitis and periodontitis . Besides, it has been reported that A. vera mouthwash reduced plaque and gingivitis, though less than chlorhexidine .