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<p>Phycocyanin (PC), a water-soluble pigment-protein complex, is well known for its wide range of biological functions. PC is composed of two polypeptide subunits, α and β, each covalently linked to linear tetrapyrrole chromophores (phycocyanobilins). These chromophores are responsible for its intense blue color and fluorescence properties, making PC an important marker in biochemical and biomedical research. This study provides comprehensive insight into the structural features and potent antioxidant (free radical scavenging) activity of PC extracted from the rice-field cyanobacterium <i>Dolichospermum spiroides</i> HKAR-23. The purification process involved successive steps of ammonium sulfate precipitation, dialysis, and ultracentrifugation, resulting in a pure (cosmetic grade) and stable pigment. This study further highlights the establishment of an effective and simplified protocol for purifying and recovering PC using sucrose-gradient ultracentrifugation. The characteristic spectral features of PC were confirmed using UV-VIS absorption spectrophotometry. Further structural and physicochemical characterization was performed using a range of analytical techniques, including nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analysis, and thermogravimetric analysis (TGA). The findings suggest that PC derived from <i>Dolichospermum spiroides</i> HKAR-23 exhibits a stable amorphous structure. The antioxidant potential of the purified PC was evaluated using DPPH, ABTS, SRSA, and FRAP assays, all of which revealed a strong, dose-dependent free radical scavenging activity. The IC<sub>50</sub> values of PC were 83.2&#xa0;µg mL<sup>− 1</sup>, 133.8&#xa0;µg mL<sup>− 1</sup>, and 109&#xa0;µg mL<sup>− 1</sup> for the DPPH, ABTS, and SRSA assays, respectively. The high purity and preserved structural integrity of PC contributed to its potent antioxidant activity. These findings highlight PC as a promising natural bioactive compound with potential applications in the nutraceutical, pharmaceutical, and cosmetic industries.</p>

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Structural characterization and free radical scavenging potential of phycocyanin isolated from the rice-field cyanobacterium Dolichospermum spiroides HKAR-23

  • 期刊论文

  • 发表日期：

    2026年2月11日

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  • Sapana Jha,
  • Varsha K. Singh,
  • Ashish P. Singh,
  • Rajeshwar P. Sinha

摘要

Phycocyanin (PC), a water-soluble pigment-protein complex, is well known for its wide range of biological functions. PC is composed of two polypeptide subunits, α and β, each covalently linked to linear tetrapyrrole chromophores (phycocyanobilins). These chromophores are responsible for its intense blue color and fluorescence properties, making PC an important marker in biochemical and biomedical research. This study provides comprehensive insight into the structural features and potent antioxidant (free radical scavenging) activity of PC extracted from the rice-field cyanobacterium Dolichospermum spiroides HKAR-23. The purification process involved successive steps of ammonium sulfate precipitation, dialysis, and ultracentrifugation, resulting in a pure (cosmetic grade) and stable pigment. This study further highlights the establishment of an effective and simplified protocol for purifying and recovering PC using sucrose-gradient ultracentrifugation. The characteristic spectral features of PC were confirmed using UV-VIS absorption spectrophotometry. Further structural and physicochemical characterization was performed using a range of analytical techniques, including nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analysis, and thermogravimetric analysis (TGA). The findings suggest that PC derived from Dolichospermum spiroides HKAR-23 exhibits a stable amorphous structure. The antioxidant potential of the purified PC was evaluated using DPPH, ABTS, SRSA, and FRAP assays, all of which revealed a strong, dose-dependent free radical scavenging activity. The IC50 values of PC were 83.2 µg mL− 1, 133.8 µg mL− 1, and 109 µg mL− 1 for the DPPH, ABTS, and SRSA assays, respectively. The high purity and preserved structural integrity of PC contributed to its potent antioxidant activity. These findings highlight PC as a promising natural bioactive compound with potential applications in the nutraceutical, pharmaceutical, and cosmetic industries.