The principal active components of Penicillium are listed in the following table:
Other minor active components of Penicillium include penicillin O, penicillin U1 and penicillin U6. Other named constituents of natural Penicillium, such as penicillin A, were subsequently found not to have antibiotic activity and are not chemically related to antibiotic penicillins.The precise constitution of the penicillin extracted depends on the species of Penicillium mould used and on the nutrient media used to culture the mould. Flemings original strain of Penicillium rubens produces principally penicillin F, named after Fleming. But penicillin F is unstable, difficult to isolate, and produced by the mould in small quantities.The principal commercial strain of Penicillium chrysogenum (the Peoria strain) produces penicillin G as the principal component when corn steep liquor is used as the culture medium. When phenoxyethanol or phenoxyacetic acid are added to the culture medium, the mould produces penicillin V as the main penicillin instead.6-Aminopenicillanic acid (6-APA) is a compound derived from penicillin G. 6-APA contains the beta-lactam core of penicillin G, but with the side chains stripped off; 6-APA is a useful precursor for manufacturing other penicillins. There are many semi-synthetic penicillins derived from 6-APA and these are in three groups: antistaphylococcal penicillins, broad-spectrum penicillins, and antipseudomonal penicillins. The semi-synthetic penicillins are all referred to as penicillins because they are all derived ultimately from penicillin G.

Penicillin units
One unit of penicillin G sodium is defined as 0.600 micrograms. Therefore, 2 million units (2 megaunits) of penicillin G is 1.2 g.
One unit of penicillin V potassium is defined as 0.625 micrograms.
A variant of the gene that encodes the neurotransmitter metabolizing enzyme monoamine oxidase-A (MAOA), which relates to neural systems involved in aggression, plays a key role in regulating behavior following threatening events. Brain imaging studies show patterns of arousal in areas of the brain that are associated with aggression in response to emotion-provoking stimuli. Prenatal factors and birth complications
Many pregnancy and birth problems are related to the development of conduct problems. Malnutrition, specifically protein deficiency, lead poisoning or exposure to lead, and mothers use of alcohol or other substances during pregnancy may increase the risk of developing ODD. In numerous research, substance use prior to birth has also been associated with developing disruptive behaviors such as ODD. Although pregnancy and birth factors are correlated with ODD, strong evidence of direct biological causation is lacking. Neurobiological factors
Deficits and injuries to certain areas of the brain can lead to serious behavioral problems in children. Brain imaging studies have suggested that children with ODD may have hypofunction in the part of the brain responsible for reasoning, judgment, and impulse control. Children with ODD are thought to have an overactive behavioral activation system (BAS), and an underactive behavioral inhibition system (BIS). The BAS stimulates behavior in response to signals of reward or non-punishment. The BIS produces anxiety and inhibits ongoing behavior in the presence of novel events, innate fear stimuli, and signals of non-reward or punishment. Neuroimaging studies have also identified structural and functional brain abnormalities in several brain regions in youths with conduct disorders.