4-Piperidinol, 1-phenethyl-4-phenyl acetate (PEPAP) is a synthetic opioid discovered by Janssen in 1960. PEPAP is an analog of meperidine, it is abused and illegally sold on streets as a "synthetic heroin".

Propionic acid (PA), also known as propanoic acid, with chemical formula C3H6O2, is an organic acid used as a food additive and found naturally on the skin and in the gastrointestinal tract. It is a byproduct of fermentation reactions and is also produced industrially from ethylene or ethanol and carbon monoxide. Propionic acid is a fungicide and bactericide, registered to controlfungi and bacteria in stored grains, hay, grain storage areas, poultry litter,and drinking water for livestock and poultry. As a food preservative, propionic acid prevents mold in bread and baked goods, and it is used as a flavoring agent in cheese and other packaged goods. The U.S. Environmental Protection Agency considers it safe and therefore, has no limitation on its use. It has been demonstrated that PA lowers fatty acids content in liver and plasma, reduces food intake, exerts immunosuppressive actions and probably improves tissue insulin sensitivity. Thus increased production of PA by the microbiota might be considered beneficial in the context of prevention of obesity and diabetes type 2. The molecular mechanisms by which PA may exert this plethora of physiological effects are slowly being elucidated and include intestinal cyclooxygenase enzyme, the G-protein coupled receptors 41 and 43 and activation of the peroxisome proliferator-activated receptor γ, in turn inhibiting the sentinel transcription factor NF-κB and thus increasing the threshold for inflammatory responses in general. Taken together, PA emerges as a major mediator in the link between nutrition, gut microbiota and physiology. The sodium salt of propionic acid was previously approved in Canada as an active ingredient in Amino-Cerv (used to treat inflammation or injury of the cervix).

Calcium propionate (E282) is a preservative, antimould and antirope agent. Calcium propionate has been widely used as a preservative in bakery and in bread. The addition of 0.3 % calcium propionate prolonged the shelf-life of salt reduced bread to 10-12 days. It is sometimes not carefully used, or a high concentration is added to preserve products. High consumption of calcium propionate can lead to several health problems. Calcium propionate is used to prevent milk fever in cows and as a feed supplement. It is considered to be safe and effective treatment given for one or two days to prevent milk fever and/or to support treatment of milk fever. Calcium propionate is generally recognized as safe by FDA when used in accordance with good manufacturing or feeding practice.

Creatinine is a product of metabolism of creatine phosphate, a molecule that serves as a rapidly mobilizable reserve of a brain and skeletal muscle. Creatinine is excreted by kidneys with little or no reabsorption. Serum creatinine is the most commonly used indicator of renal function.

Estradiol an aromatized C18 steroid with hydroxyl group at 3-beta- and 17-beta-position. Estradiol-17-beta is the most potent form of mammalian estrogenic steroids. In humans, it is produced primarily by the cyclic ovaries and the placenta. It is also produced by the adipose tissue of men and postmenopausal women. The 17-alpha-isomer of estradiol binds weakly to estrogen receptors (receptors, estrogen) and exhibits little estrogenic activity in estrogen-responsive tissues. Estradiol enters target cells freely (e.g., female organs, breasts, hypothalamus, pituitary) and interacts with a target cell receptor. When the estrogen receptor has bound its ligand it can enter the nucleus of the target cell, and regulate gene transcription which leads to formation of messenger RNA. The mRNA interacts with ribosomes to produce specific proteins that express the effect of estradiol upon the target cell. Estradiol is used for the treatment of urogenital symptoms associated with post-menopausal atrophy of the vagina (such as dryness, burning, pruritus and dyspareunia) and/or the lower urinary tract (urinary urgency and dysuria). Estradiol is marketed under the brand name Climara (among others), indicated for: the treatment of moderate to severe vasomotor symptoms due to menopause, treatment of symptoms of vulvar and vaginal atrophy due to menopause, treatment of hypoestrogenism due to hypogonadism, castration or primary ovarian failure and prevention of postmenopausal osteoporosis.

Testosterone is a steroid sex hormone found in both men and women. In men, testosterone is produced primarily by the Leydig (interstitial) cells of the testes when stimulated by luteinizing hormone (LH). It functions to stimulate spermatogenesis, promote physical and functional maturation of spermatozoa, maintain accessory organs of the male reproductive tract, support development of secondary sexual characteristics, stimulate growth and metabolism throughout the body and influence brain development by stimulating sexual behaviors and sexual drive. In women, testosterone is produced by the ovaries (25%), adrenals (25%) and via peripheral conversion from androstenedione (50%). Testerone in women functions to maintain libido and general wellbeing. Testosterone exerts a negative feedback mechanism on pituitary release of LH and follicle-stimulating hormone (FSH). Testosterone may be further converted to dihydrotestosterone or estradiol depending on the tissue. The effects of testosterone in humans and other vertebrates occur by way of two main mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors. Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5α-reductase. DHT binds to the same androgen receptor even more strongly than T, so that its androgenic potency is about 2.5 times that of T. The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects. Testosterone is used as hormone replacement or substitution of diminished or absent endogenous testosterone. Use in males: For management of congenital or acquired hypogonadism, hypogonadism associated with HIV infection, and male climacteric (andopause). Use in females: For palliative treatment of androgen-responsive, advanced, inoperable, metastatis (skeletal) carcinoma of the breast in women who are 1-5 years postmenopausal; testosterone esters may be used in combination with estrogens in the management of moderate to severe vasomotor symptoms associated with menopause in women who do not respond to adequately to estrogen therapy alone.

Propionic acid (PA), also known as propanoic acid, with chemical formula C3H6O2, is an organic acid used as a food additive and found naturally on the skin and in the gastrointestinal tract. It is a byproduct of fermentation reactions and is also produced industrially from ethylene or ethanol and carbon monoxide. Propionic acid is a fungicide and bactericide, registered to controlfungi and bacteria in stored grains, hay, grain storage areas, poultry litter,and drinking water for livestock and poultry. As a food preservative, propionic acid prevents mold in bread and baked goods, and it is used as a flavoring agent in cheese and other packaged goods. The U.S. Environmental Protection Agency considers it safe and therefore, has no limitation on its use. It has been demonstrated that PA lowers fatty acids content in liver and plasma, reduces food intake, exerts immunosuppressive actions and probably improves tissue insulin sensitivity. Thus increased production of PA by the microbiota might be considered beneficial in the context of prevention of obesity and diabetes type 2. The molecular mechanisms by which PA may exert this plethora of physiological effects are slowly being elucidated and include intestinal cyclooxygenase enzyme, the G-protein coupled receptors 41 and 43 and activation of the peroxisome proliferator-activated receptor γ, in turn inhibiting the sentinel transcription factor NF-κB and thus increasing the threshold for inflammatory responses in general. Taken together, PA emerges as a major mediator in the link between nutrition, gut microbiota and physiology. The sodium salt of propionic acid was previously approved in Canada as an active ingredient in Amino-Cerv (used to treat inflammation or injury of the cervix).