Naturally Occurring Functional Ingredient from Filamentous Thermophilic Cyanobacterium Leptolyngbya sp. KC45: Phytochemical Characterizations and Their Multiple Bioactivities

Abstract

Cyanobacteria are rich in phytochemicals, which have beneficial impacts on the prevention of many diseases. This study aimed to comprehensively characterize phytochemicals and evaluate multifunctional bioactivities in the ethanolic extract of the cyanobacterium Leptolyngbya sp. KC45. Results found that the extract mainly contained chlorophylls, carotenoids, phenolics, and flavonoids. Through LC-ESI-QTOF-MS/MS analysis, 38 phenolic compounds with promising bioactivities were discovered, and a higher diversity of flavonoids was found among the phenolic compounds identified. The extract effectively absorbed the harmful UV rays and showed high antioxidant activity on DPPH, ABTS, and PFRAP. The extract yielded high-efficiency inhibitory effects on enzymes (tyrosinase, collagenase, ACE, and α-glucosidase) related to diseases. Interestingly, the extract showed a strong cytotoxic effect on cancer cells (skin A375, lung A549, and colon Caco-2), but had a much smaller effect on normal cells, indicating a satisfactory level of safety for the extract. More importantly, the combination of the DNA ladder assay and the TUNEL assay proved the appearance of DNA fragmentation in cancer cells after a 48 h treatment with the extract, confirming the apoptosis mechanisms. Our findings suggest that cyanobacterium extract could be potentially used as a functional ingredient for various industrial applications in foods, cosmetics, pharmaceuticals, and nutraceuticals.

Keywords: bioactivity; cyanobacteria; ethanolic extract; functional ingredient; phytochemicals.

Figure 1

Ultraviolet–visible (UV–Vis) absorption spectra of the ethanolic extract from cyanobacteria, Leptolyngbya sp. KC45.

Figure 2

The gallic acid equivalent antioxidant capacity (mg-GAE/g-extract) (a) and the half maximal inhibitory concentration (IC₅₀; mg/mL) on 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), and potassium-ferricyanide-reducing antioxidant power (PFRAP) (b) of the ethanolic extract from cyanobacteria, Leptolyngbya sp. KC45.

Figure 3

The half maximal inhibitory concentration (IC₅₀) (a) and the equivalent standard compound capacity (b) of the ethanolic extract from cyanobacteria, Leptolyngbya sp. KC45 on enzyme inhibitory activity.

Figure 4

The cytotoxicity of skin cancer A375 cells, lung cancer A549 cells, and colon cancer Caco-2 cells after treatment with the ethanolic extract from cyanobacteria, Leptolyngbya sp. KC45 when compared with control cells, i.e., normal Vero cells, for 48 h. Cell viability was measured using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction (MTT) assay (a) and calculated for comparisons with the control cells (b).

Figure 5

Morphology of skin cancer A375 cells, lung cancer A549 cells, colon cancer Caco-2 cells, and normal Vero cells after treatment with the ethanolic extract from cyanobacteria, Leptolyngbya sp. KC45, when compared with control (untreated) cells for 48 h.

Figure 6

Deoxyribonucleic acid (DNA) fragmentation of skin cancer A375 cells, lung cancer A549 cells, and colon cancer Caco-2 cells after treatment with the ethanolic extract from cyanobacteria, Leptolyngbye sp. KC45, for 48 h when compared with control cells, i.e., normal Vero cells, by agarose gel electrophoresis (a) and inverting (black/white) the agarose gel (b).

Figure 7

Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay of skin cancer A375 cells, lung cancer A549 cells, and colon cancer Caco-2 cells after treatment with the ethanolic extract from cyanobacteria, Leptolyngbya sp. KC45, when compared with control cells, i.e., normal Vero cells, for 48 h. The cells were stained with 4′,6-diamidino-2-phenylindole (DAPI) and TUNEL, and observed under a fluorescent microscope.