Retinal, All-trans is one of the forms of vitamin A. It is an isomer of 11-cis-retinal, transductor of light into the neural signals. Retinal, All-trans is converted to retinoic acid in vivo by the action of retinal dehydrogenase. Retinal, All-trans is associated with one of the two isoforms of cellular retinol-binding proteins (CRBP-I and CRBP-II). These proteins play important roles in retinoid biology and regulation of the metabolism of retinol and retinal.

Bilirubin is an orange-yellow pigment made during the normal breakdown of red blood cells. Bilirubin passes through the liver and is excreted out of the body. Occasionally, higher bilirubin levels may indicate an increased rate of destruction of red blood cells (hemolysis). A high level of bilirubin in the blood is called hyperbilirubinemia. High bilirubin levels can cause jaundice. Jaundice makes the skin and the whites of the eyes appear yellow, due to the brown and yellow bilirubin in the blood. Phototherapy for neonatal is one of the treatment methods against hyperbilirubinemia. Light absorption by bilirubin in the skin transforms the native Z,Z-bilirubin to conformational photoisomers Z,E-bilirubin and E,Z-bilirubin and structural photoisomers E,Z-lumirubin and E,E-lumirubin. Formation and excretion of Z,E-bilirubin and E,Z-lumirubin are both important routes of elimination of bilirubin through bile and urine, although the precise contributions of the various photoisomers to the overall elimination of bilirubin are still unknown.

Lanosterol represents the first step in sterol formation and can be converted by lanosterol 14 α-demethylase (CYP51, a member of the cytochrome P450 family), to follicular fluid meiosis activating factor (FF-MAF), a sterol intermediate that has been extensively studied and shown to activate meiosis in gametes. Lanosterol modulates TLR4-mediated innate immune responses in macrophages. Lanosterol accumulation increases membrane fluidity and ROS production, thus potentiating phagocytosis and the ability to kill bacteria. Preliminary studies in dogs and rabbits have shown that lanosterol can prevent and even reverse cataract formation. However, Lanosterol 25 mM solution did not reverse opacification of human age-related cataractous nuclei. Lanosterol induces mitochondrial uncoupling and protects dopaminergic neurons from cell death in a model for Parkinson's disease.

Trimethylamine (or TMA) a tertiary amine, is synthesized by the action of microbial enzymes in humans. The decrease of TMA metabolism and excessive TMA excretion cause the disease trimethylaminuria and some other diseases associated with the abnormal level of TMA, e.g., obesity, diabetes, cardiovascular diseases. It was shown, that TMS is a full agonist of human trace amine-associated receptor 5, TAAR5. In addition, TMA is a precursor of N-oxide form, an emergent biomarker of human health that can lead to renal diseases, neurological disorders, and cancer.

SERINE, D- (D-serine) is a non-essential amino acid occurring in natural form as the L-isomer. It is synthesized from glycine or threonine. It is involved in the biosynthesis of purines, pyrimidines and other amino acids. A considerable level of D-serine was discovered, surprisingly, in the mammalian brain in the early 1990s. Since then, D-serine has been considered to be a co-agonist of glutamate at the glycine site of NMDA receptors. D-serine plays an important role in the central nervous system as an endogenous ligand for the glycine site of glutamate N-Methyl-D-Aspartate (NMDA) receptors. D-serine is synthetized by racemization of L-serine in most neural and non-neural cells, and modulates a variety of physiological functions in mammals. D-Serine synthesis is attributed to Serine Racemase (SR), which catalyses the synthesis of D-serine from L-serine. D-serine may play a role in the pathophysiology of neuropsychiatric disorders, such as schizophrenia, which may be linked to NMDA receptor hypo-function. Studies in genetic and pharmacological animal models with decreased D-serine levels have shown that these animals displayed behavioural abnormalities similar to those seen in schizophrenia. Moreover, exogenous administration of D-serine and related compounds improved several phenotypes relevant to schizophrenia, which could have positive clinical implications in humans. The results of a clinical trial in Taiwanese schizophrenic patients who received D-serine as adjuvant treatment indicated that those patients who received D-serine treatment, improved positive, negative and cognitive symptoms seen in schizophrenia. In addition, this clinical trial showed that D-serine did not worsen side effects from other antipsychotics, which may be due to its selective action at the NMDA-glycine site. Therefore, D-serine could be considered as a therapeutic approach for schizophrenia, which is different from the dopaminergic approach. It has also been shown that exogenous d-serine administration can suppress appetite and alter food preference. Thus NMDA receptor and its co-agonist d-seine participate in the control of appetite and food preference, which can be used to suppress obesity. D-serine has been shown to have cognitive-enhancing properties in different brain disorders and in age-related cognitive decline. From a clinical perspective, it is important to highlight that in a recent double-blind placebo-controlled cross-over study our group observed that an acute oral administration of 30 mg/kg of d-serine improved spatial learning and problem solving. D-serine may be especially useful for depression because of its acute and chronic antidepressant effects,

Estriol (E3), also spelled oestriol, is a steroid, a weak agonist of the estrogen receptors ERα and ERβ., and a minor female sex hormone. According to in vitro study, the relative binding affinity (RBA) of estriol for the human ERα and ERβ was 11.3% and 17.6% of that estradiol, respectively, and the relative transactivational capacity of estrone at the ERα and ERβ was 10.6% and 16.6% of that of estradiol, respectively. Estriol is marketed widely in Europe and elsewhere throughout the world under the brand names Ovestin, Ortho-Gynest, and a variety of others. It is available in oral tablet, vaginal cream, and vaginal suppository form, and is used in menopausal hormone therapy for the treatment of menopausal symptoms. Estriol is also available in some countries as estriol succinate (brand name Synapause), a dosage-equivalent ester prodrug of estriol. Estriol and estriol succinate are not approved for use in the United States and Canada, although they have been produced and sold by compounding pharmacies in North America for use as a component of bioidentical hormone therapy. Estriol can be measured in maternal blood or urine and can be used as a marker of fetal health and well-being. If levels of unconjugated estriol (uE3 or free estriol) are abnormally low in a pregnant woman, this may indicate chromosomal or congenital anomalies like Down syndrome or Edward's syndrome. It is included as part of the triple test and quadruple test for antenatal screening for fetal anomalies.

Cytosine is a pyrimidine nucleobase, one of the five main bases of nucleic acids. In DNA and RNA cytosine is paired with guanine. Only small amounts of cytosine administered with food are incorporated in DNA. The majority of cytosine is synthesized de-novo starting from carbamoyl phosphate.