Correct option is A
Explanation-
Dirigent proteins are non-enzymatic proteins involved in stereoselective coupling of phenoxy radicals. They do not catalyze the formation of radicals but guide the specific stereochemistry of coupling between radicals produced by oxidative enzymes like peroxidases. These proteins were first discovered in Forsythia intermedia, guiding the formation of specific lignan stereoisomers. Lignans are a type of phenolic compound derived from the coupling of two monolignol units (like coniferyl alcohol). They are found in plants. They strengthen the cell wall, act as defense compounds and serve as precursors for other bioactive molecules.
Incorrect options -
Option b - Alkaloids - Alkaloids are nitrogen-containing compounds. Dirigent proteins are not involved in their biosynthesis.
Option c - Terpenoids - Terpenoids are synthesized via the MVA/MEP pathway. Dirigent proteins are not relevant here.
Option d - Amino acids - Dirigent proteins are not part of primary metabolism like amino acid synthesis.
Final answer : Option a - Lignans
