Capsaicin Biosynthesis Research Articles

Activity of Enzymes Involved in Capsaicin Biosynthesis in Callus Tissue and Fruits of Chili Pepper ( Capsicum annuum L.)

In order to examine the functionality of the capsaicinoid biosynthetic pathway in callus cultures of chili pepper (Capsicum annuum L.), we investigated the enzyme activity of phenylalanine ammonia-lyase (PAL), cinnamic acid-4-hydroxylase (CA4H), p-coumaric acid-3-hydroxylase (CA3H), caffeic acid-O-methyltransferase (CAOMT) and capsaicinoid synthetase (CS). These enzymes were also determined in developing and mature fruits. The maximum activities of PAL, CA4H and CA3H in callus cultures were similar to those of chili pepper fruits, but the values of CAOMT and CS were 6 times lower than those of fruits. The significance of these data in relation to capsaicin accumulation is discussed.

Phenylalanine ammonia‐lyase activity and capsaicin‐precursor compounds in p‐fluorophenylalanine‐resistant and ‐sensitive variant cells of chili pepper (Capsicum annuum)

Cell suspension cultures of chili pepper (Capsicum annuum L. cv. Tampiqueño 74) displaying differences in their resistance to p‐fluorophenylalanine (PFP) and in their contents of capsaicin (the compound which is responsible for the hot taste of chili pepper fruits) were characterized in relation to the activity of phenylalanine ammonia‐lyase (PAL; EC 4.3.1.5), the levels of free l‐phenylalanine, phenolics and the phenylpropanoid acids involved in capsaicin biosynthesis. A nonselected cell line, a sensitive line (CA‐02), a moderately resistant cell line (CA‐29) and two resistant cell lines (CA‐04 and CA‐16) were studied. Higher PAL activities and higher levels of phenylalanine and phenolics were found in the PFP‐resistant cells even after a minimum of 9 subcultures (15 days each) in the absence of the analog, indicating that the selected trait was stable. PFP‐resistant chili pepper cells accumulated higher amounts of capsaicin precursors (cinnamic, caffeic and ferulic acids) than either the nonselected cells or the sensitive cell line. p‐Coumaric acid was not detected at significant levels in any of the cell cultures. Overall, accumulation of free phenyl‐alanine correlated well with PAL activity, phenolics, phenylpropanoids and capsaicin levels, suggesting an active flow through the phenylpropanoid pathway in PFP‐resistant cells of chili pepper.

The accumulation of phenylpropanoid and capsaicinoid compounds in cell cultures and whole fruit of the chilli pepper, Capsicum frutescens Mill

The accumulation of the phenylpropanoid precursors of capsaicin in suspended and immobilised cell cultures of C. frutescens has been studied and compared with accumulation in whole pepper fruit. The use of HPLC techniques has revealed that the phenolic precursors of capsaicin are present in chilli pepper cells at extremely low levels, irrespective of the source of tissue or the developmental state. Radioactive tracer studies have indicated that the majority of the phenolic derivatives of phenylalanine are ultimately bound to the insoluble fraction of the cells. Results from experiments where immobilised cell cultures were grown under conditions which enhance capsaicin yield would suggest that the ‘diversion’ of compounds into this bound fraction has a considerable influence upon capsaicin biosynthesis in this system.

Intracellular distributions of enzymes and intermediates involved in biosynthesis of capsaicin and its analogues in Capsicum fruits.

Phenylalanine ammonia-lyase, trans-cinnamate 4-monooxygenase, and capsaicinoid synthetase [Agric. Biol. Chem., 44, 2907 (1980)] activities were investigated in the subcellular fractions from protoplasts of placenta of Capsicum fruits. The subcellular distribution of intermediates of the capsaicinoid biosynthesis, trans-cinnamic acid and trans-p-coumaric acid, and capsaicinoid were also investigated. The activity of trans-cinnamate 4-monooxygenase and capsaicinoid synthetase was in the vacuole fraction. While the activity of phenylalanine ammonia-lyase was in the cytosol fraction. After feeding l-[U-14C]phenylalanine to the protoplast, the newly synthesized trans-p-coumaric acid and capsaicinoid were found in the vacuole fraction, while trans-cinnamic acid was not in the vacuole fraction. The possible role of the vacuole on the biosynthesis of capsaicinoid is also discussed.

Biosynthesis of capsaicin and dihydrocapsaicin in Capsicum frutescens.

Biosynthesis of capsaicin and dihydrocapsaicin in Capsicum frutescens.

Constitution and biosynthesis of capsaicin

Capsaicin, the crystalline pungent principle of Capsicum annuum, has been shown to be a mixture of at least five closely related vanillyl amides. Phenylalanine, various hydroxylated cinnamic acids, and vanillylamine, all labelled with tritium in the aromatic ring, were incorporated biosynthetically into the C6–C1 unit of capsaicin. Tyrosine was incorporated much less efficiently than phenylalanine. The radioactive capsaicin mixture derived biosynthetically from phenylalanine was found to contain most of the activity in the minor, saturated components.