Tomatidine is the aglycone derivative of tomatine. Tomatidine belongs to the chemical family known as Spirosolanes and Derivatives. These are steroidal alkaloids whose structure contains a spirosolane skeleton. Tomatine (the glycosylated form of tomatidine) is a mildly toxic glycoalkaloid or glycospirosolane found in the stems and leaves of tomato plants as well as in the fruit of unripened (green) tomatoes (up to 500 mg/kg).

Red, ripe tomatoes have somewhat reduced amounts of tomatine and tomatidine. Both tomatine and tomatidine possess antimicrobial, antifungal and antiviral properties. Tomatidine has been shown to exhibit anti-virulence activity against normal strains of Staphylococcus aureus as well as the ability to potentiate the effect of aminoglycoside antibiotics. Recent studies have shown that tomatidine stimulates mTORC1 signaling and anabolism, leading to accumulation of protein and mitochondria, and ultimately, cell growth. Furthermore, in mice, tomatidine has been shown to increase skeletal muscle mTORC1 signaling, reduce skeletal muscle atrophy, enhance recovery from skeletal muscle atrophy, stimulate skeletal muscle hypertrophy, and increase strength and exercise capacity. Tomatidine has also been shown to significantly inhibit cholesterol ester accumulation induced by acetylated LDL in human monocyte-derived macrophages in a dose-dependent manner. Tomatidine also inhibits cholesterol ester formation in Chinese hamster ovary cells overexpressing acyl-CoA:cholesterol acyl-transferase (ACAT)-1 or ACAT-2, suggesting that tomatidine suppresses both ACAT-1 and ACAT-2 activities. The oral administration of tomatidine to apoE-deficient mice significantly reduces levels of serum cholesterol, LDL-cholesterol, and the size of atherosclerotic lesions.