The selective serotonin reuptake inhibitor fluoxetine consists of equal amounts of R and S stereoisomers (antidepressant Prozac (racemic fluoxetine). Binding to the transporter confirmed selectivity of R- and S-fluoxetine for the 5-HT transporter versus the dopamine (DA) and norepinephrine (NE) human transporters. In addition, receptor binding studies demonstrated significant affinity of R-fluoxetine, but not S-fluoxetine, for human 5-HT(2A) and 5-HT(2C) receptor subtypes. R-fluoxetine acts as an antagonist at 5-HT(2A) and 5-HT(2C) receptors. The attempt to develop a single-enantiomer formulation of fluoxetine for the treatment of depression was unsuccessful. Eli Lilly has terminated its licensing and development agreement with Marlborough, Mass.-based Sepracor for (R)-fluoxetine, the single-isomer version of Lilly's antidepressant Prozac.R-enantiomer of fluoxetine, at its highest administered dose, led to statistically significant prolongation of cardiac repolarization in phase II studies; the studies were subsequently stopped.

Mesaconitine is a diterpene alkaloid, from the plants of the Aconitum genus, Ranunculaceae. Mesaconitine is a centrally acting analgesic without affinity to opioid receptors. It has been reported that the antinociception is due to an interaction with the noradrenergic system. As a neurotoxic, it opens the TTX-sensitive Na+ channels in the heart and other tissues and induces arrhythmia. The activity of Mesaconitine, which is a chemical analog of Aconitine, on TTX sensitive Na+ channels in the heart and other tissues is stronger than that of Aconitine. The duration of its neurotoxic effect is shorter. It possesses an hypotensive activity. The hypotensive action is not inhibited by an adrenergic b-blocker but abolished with muscarinic blocker. It may be partially mediated by a muscarinic mechanism. Mesaconitine binds with high affinity to the open state of the voltage-sensitive sodium channels at site 2, thereby causing a persistent activation of the sodium channels, which become refractory to excitation.

N‑Nitrosonornicotine (NNN) is a nitrosamine compound. It is produced by nitrosation of nicotine during the curing, aging, processing, and smoking of tobacco. About half of the NNN originates in the unburnt tobacco, whereas the remainder is formed during burning. NNN is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals. NNN induces deleterious mutations in oncogenes and tumor suppression genes by forming DNA adducts, which could be considered as tumor initiation. Meanwhile, the binding of NNN to the nicotinic acetylcholine receptor promotes tumor growth by enhancing and deregulating cell proliferation, survival, migration, and invasion, thereby creating a microenvironment for tumor growth.

Pseudohypericin is a predominant naphthodianthrone from St. John’s wort (Hypericum perforatum L.) phytomedicinal drug. It has been shown to specifically inhibit protein kinase C and dopamine-β-hydroxylase. Also, pseudohypericin induces apoptosis and selectively antagonizes corticotropin-releasing factor in murine models. Inhibition of thioredoxin system by pseudohypericin showed appreciable anticancer properties of this natural compound. Pseudohypericin has antiretroviral activity, it has potential therapeutic value in diseases such as AIDS. Pseudohypericin is implicated in the antidepressant efficacy of St. John's wort.

Asarinin, an urofuran lignan, is the epimer of sesamin. Asarinin is listed in Chinese Pharmacopoeia and used as a quality control (QC) index of crude herbs by the State Food and Drug Administration of China. Asarinin exhibits several biological activities such as decreasing cholesterol levels, exhibiting antihypertensive and antiangiogenic properties and providing immunosuppressive and hepatoprotective activities. Asarinin can also inhibit myocardial injury in metabolic syndrome of rats and decrease the possibility of acute heart transplant rejection. Sesamin was first isolated from sesame seed oil, while asarinin was first isolated from prickly ash bark. Both sesamin and asarinin have been shown to act as insecticidal synergists with pyrethrins.

(Z)-Guggulsterone is a natural product that lowers cholesterol due to its function as an antagonist ligand for the bile acid receptor. (Z)-Guggulsterone is a nuclear hormone receptor that regulates the transcription of several genes involved in cholesterol metabolism and plays a role in cholesterol level regulation. (Z)-Guggulsterone is also a selective farnesoid X receptor (FXR) modulator. Both Guggulsterone isomers were demonstrated to suppress lipopolysaccharide-induced inflammation by inhibiting IκB-α degradation and NF-κB activation. GS has medicinal properties such as anti-inflammatory, hepatoprotective, muscle relaxing, hypocholesterolemic and anti-obesity, antimycobacterial, antischistomal, larvicidal, and molluscicida.