Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is a flavonoid found in many edible plants (e.g. tea, broccoli, cabbage, kale, beans, endive, leek, tomato, strawberries and grapes) and in plants or botanical products commonly used in traditional medicine (e.g. Ginkgo biloba, Tilia spp, Equisetum spp, Moringa oleifera, Sophora japonica and propolis). Numerous preclinical studies have shown that kaempferol and some glycosides of kaempferol have a wide range of pharmacological activities, including antioxidant, anti-inflammatory, antimicrobial, anticancer, cardioprotective, neuroprotective, antidiabetic, anti-osteoporotic, estrogenic/antiestrogenic, anxiolytic, analgesic and antiallergic activities.

5-(2-Aminopropyl)indole (5-API, 5-IT, PAL-571) is a psychoactive phenethylamine derivative with empathogenic effects used for recreational purposes. 5-(2-Aminopropyl)indole, originally synthesized as a stimulant in the 1960s now joins the list of psychoactive substances and may to be one of the newest MDMA replacements. 5-(2-Aminopropyl)indole acts as a triple monoamine releasing agent and also as selective MAO-A inhibitor.

Isatin (1H-indole-2,3-dione) is a naturally occurring heterocycle that was first synthesised by Erdmann and Laurent in 1840. Isatin possesses a wide range of biological activities. Isatin has anxiogenic, sedative, anticonvulsant activities and acts as a potent antagonist on atrial natriuretic peptide receptors in vitro. Isatin is an endogenous monoamine oxidase (MAO) inhibitor involved in stress and anxiety. Additionally, isatin inhibits alkaline phosphatase (ALP), nitric oxide (NO)-stimulated soluble guanylate cyclase, and other enzymes.

Salsolidine is a simple 1-substituted tetrahydroisoquinoline isolated from many natural sources as the racemate and in its enantiomeric modifications. Stereoselective competitive inhibition of MAO A was found with the R enantiomer of salsolidine (Ki = 6 uM). Salsolidine also inhibits acetylcholinesterase (AChE), and buytlcholinesterase (BChE). Salsolidine may inhibit catechol-O-methyltransferase (COMT). Derivatives of salsolidine are neurotoxic and cytotoxic. R enantiomer of salsolidine is more potent than the S form.

Norharman or beta-carboline (9H-pyrido[3,4-b]indole) is a neuroactive alkaloid first isolated from Peganum harmala L. It is implicated in a number of human diseases including Parkinson's disease, tremor, addiction and cancer. Norharman formed endogenously but external sources have been identified (among others fried meat and fish, meat extracts, alcoholic drinks, coffee brews, tobacco smoke). It inhibits monoamine oxidase and indoleamine 2,3-dioxygenase. In addition norharman binds with high affinity to imidazoline I2B receptors. Plasma norharman levels are elevated in chronic alcoholics and Parkinson's disease patients.

1,4-naphthoquinone is a chemical studied as a potential inhibitor of monoamine oxidase and DNA topoisomerase activities as well as acetyltransferase activity. 1,4-Naphthoquinone is a potent inhibitor of human cancer cell growth and angiogenesis.

Jatrorrhizine is an active component of the traditional Chinese herb Coptis chinensis, which has been used to prevent and treat metabolic disorders. It is also found plants such as Enantia chlorantha, Thalictrum lucidumm, Thalictrum revolutum. Jatrorrhizine possesses antifungal, antibacterial activity. It has low toxicity and was studied in mouse models of obesity and hypercholesterolemia. The mechanism of action of Jatrorrhizine is not fully elucidated. The compound blocks alpha-1 and alpha-2 adrenoreceptors, monoamine oxidase A and B.