Biochemistry

• Aflatoxins (notably $B_1, B_2, G_1, G_2$) are highly toxic difuranocoumarin mycotoxins and Group 1 human hepatocarcinogens.
• They are synthesized primarily by Aspergillus species, predominantly Aspergillus flavus and Aspergillus parasiticus, which contaminate groundnuts, maize, tree nuts, and oilseeds under warm, humid post-harvest storage.
• Fusarium produces trichothecenes and fumonisins, while Salmonella is a bacterial enteric pathogen.
• Hence, aflatoxin is produced by Aspergillus species (Option 1).

• Clostridium perfringens (Type A) produces a lethal necrotizing, hemolytic exotoxin known as alpha ($\alpha$) toxin.
• Chemically, alpha-toxin is a zinc-dependent phospholipase C (lecithinase) that hydrolyzes phosphatidylcholine and sphingomyelin in eukaryotic cell membranes, leading to cell lysis, tissue necrosis, and gas gangrene.
• Listeria monocytogenes secretes listeriolysin O, while Salmonella typhi produces typhoid toxin.
• Therefore, Clostridium perfringens produces alpha toxin (Option 3).

• In the human liver, ingested alcohols undergo Phase-I oxidative detoxification.
• Ethyl alcohol is sequentially oxidized by Alcohol Dehydrogenase (ADH) to acetaldehyde, and by Aldehyde Dehydrogenase (ALDH) to non-toxic acetic acid:
  $$\text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{ADH}} \text{CH}_3\text{CHO} \xrightarrow{\text{ALDH}} \text{CH}_3\text{COOH}$$
• Methyl alcohol is similarly oxidized by hepatic ADH and ALDH to formaldehyde and formic acid.
• Therefore, alcohols are metabolized and detoxified via oxidation (Option 1).

Gammaxane (also commercially known as Lindane, BHC, or 666) is 1,2,3,4,5,6-hexachlorocyclohexane with the molecular formula $\text{C}_6\text{H}_6\text{Cl}_6$.

• Preparation: Synthesized by the addition reaction of three moles of chlorine gas ($\text{Cl}_2$) to benzene in the presence of ultraviolet (UV) light or sunlight:
  $$\text{C}_6\text{H}_6 + 3\text{Cl}_2 \xrightarrow{h\nu} \text{C}_6\text{H}_6\text{Cl}_6$$
• Stereoisomerism: Exists as multiple stereoisomers; the gamma ($\gamma$) isomer (known as Lindane) exhibits the highest insecticidal efficacy.
• Misnomer: Often historically called 'benzene hexachloride' (BHC), though structurally it is a saturated cyclohexane ring (not an aromatic benzene derivative).
• Environmental Impact: Banned or severely restricted in modern agriculture due to bioaccumulation and persistent environmental toxicity.