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Background <p>Elicitation is a widely used strategy to enhance secondary metabolite production in medicinal plants. However, the comparative effectiveness of different redox-modulating elicitors and their interactions in regulating antioxidant systems and terpenoid indole alkaloid (TIA) biosynthesis remains insufficiently understood.</p> Objectives <p>This study aimed to evaluate and compare the effects of hydrogen peroxide (H) in combination with melatonin (MT) or L-cysteine (Cys) on redox stability, antioxidant defense, phenolic metabolism, and TIA accumulation in <i>Catharanthus roseus in vitro</i> plants.</p> Methods <p>In vitro–grown plants were treated with H₂O₂ (H: 20 µM) alone or combined with different concentrations of MT (100, 200 and 400 µM) or Cys (200, 400 and 800 µM). Photosynthetic pigments, antioxidant enzyme activities (CAT, POD, SOD), oxidative stress indicators (H₂O₂, MDA), total phenolic content (TPC) and total flavonoid content (TFC), antioxidant capacity (TAC, FRAP), phenylpropanoid enzymes (PAL, PPO), and major alkaloids (vincristine, vinblastine, ajmalicine) were quantified using spectrophotometric and HPLC analyses.</p> Results <p>All treatments significantly enhanced antioxidant capacity and secondary metabolite accumulation compared with the control. Cys400 + H treatment was most effective for promoting biomass accumulation, activating antioxidant enzymes and TAC, whereas MT200 + H effectively enhanced TPC and minimized oxidative damage. MT400 + H preferentially improved chlorophyll content, while Cys800 + H strongly promoted carbohydrates accumulation and vincristine production. The highest plant growth, TFC and vinblastine content was recorded under H treatment alone. Ajmalicine content decreased under all elicitation regimes, indicating a redirection of metabolic flux within the TIA pathway.</p> Conclusion <p>The results demonstrate that H in combination with MT or Cys differentially modulates redox balance and metabolic flux, enabling selective enhancement of antioxidant enzymes and valuable alkaloids. Optimized elicitor combinations therefore provide an effective strategy for targeted metabolic engineering of <i>C. roseus</i> under in vitro conditions.</p>

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Synergistic effects of H2O2, melatonin, and L-cysteine on biochemical traits and alkaloid accumulation in Catharanthus roseus L. “Ocellatus” in vitro plants

  • 期刊论文

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  • 发表日期：

    2026年1月28日

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  • Elham Jafarpour,
  • Mohsen Sanikhani,
  • Azizollah Kheiry,
  • Farhang Razavi

摘要

Background

Elicitation is a widely used strategy to enhance secondary metabolite production in medicinal plants. However, the comparative effectiveness of different redox-modulating elicitors and their interactions in regulating antioxidant systems and terpenoid indole alkaloid (TIA) biosynthesis remains insufficiently understood.

Objectives

This study aimed to evaluate and compare the effects of hydrogen peroxide (H) in combination with melatonin (MT) or L-cysteine (Cys) on redox stability, antioxidant defense, phenolic metabolism, and TIA accumulation in Catharanthus roseus in vitro plants.

Methods

In vitro–grown plants were treated with H₂O₂ (H: 20 µM) alone or combined with different concentrations of MT (100, 200 and 400 µM) or Cys (200, 400 and 800 µM). Photosynthetic pigments, antioxidant enzyme activities (CAT, POD, SOD), oxidative stress indicators (H₂O₂, MDA), total phenolic content (TPC) and total flavonoid content (TFC), antioxidant capacity (TAC, FRAP), phenylpropanoid enzymes (PAL, PPO), and major alkaloids (vincristine, vinblastine, ajmalicine) were quantified using spectrophotometric and HPLC analyses.

Results

All treatments significantly enhanced antioxidant capacity and secondary metabolite accumulation compared with the control. Cys400 + H treatment was most effective for promoting biomass accumulation, activating antioxidant enzymes and TAC, whereas MT200 + H effectively enhanced TPC and minimized oxidative damage. MT400 + H preferentially improved chlorophyll content, while Cys800 + H strongly promoted carbohydrates accumulation and vincristine production. The highest plant growth, TFC and vinblastine content was recorded under H treatment alone. Ajmalicine content decreased under all elicitation regimes, indicating a redirection of metabolic flux within the TIA pathway.

Conclusion

The results demonstrate that H in combination with MT or Cys differentially modulates redox balance and metabolic flux, enabling selective enhancement of antioxidant enzymes and valuable alkaloids. Optimized elicitor combinations therefore provide an effective strategy for targeted metabolic engineering of C. roseus under in vitro conditions.