Lysophosphatidylcholines and Chlorophyll-Derived Molecules from the Diatom Cylindrotheca closterium with Anti-Inflammatory Activity

Abstract

Microalgae have been shown to be excellent producers of lipids, pigments, carbohydrates, and a plethora of secondary metabolites with possible applications in the pharmacological, nutraceutical, and cosmeceutical sectors. Recently, various microalgal raw extracts have been found to have anti-inflammatory properties. In this study, we performed the fractionation of raw extracts of the diatom Cylindrotheca closterium, previously shown to have anti-inflammatory properties, obtaining five fractions. Fractions C and D were found to significantly inhibit tumor necrosis factor alpha (TNF-⍺) release in LPS-stimulated human monocyte THP-1 cells. A dereplication analysis of these two fractions allowed the identification of their main components. Our data suggest that lysophosphatidylcholines and a breakdown product of chlorophyll, pheophorbide a, were probably responsible for the observed anti-inflammatory activity. Pheophorbide a is known to have anti-inflammatory properties. We tested and confirmed the anti-inflammatory activity of 1-palmitoyl-sn-glycero-3-phosphocholine, the most abundant lysophosphatidylcholine found in fraction C. This study demonstrated the importance of proper dereplication of bioactive extracts and fractions before isolation of compounds is commenced.

Keywords: Cylindrotheca closterium; anti-inflammatory; diatoms; drug discovery; marine biotechnology.

Figure 1

Anti-inflammatory assay. Inhibition of TNF-α secretion from LPS-stimulated THP-1 cells treated with fractions A, B, C, D, and E of Cylindrotheca closterium extracts (n = 3, ** for p < 0.01 and *** for p < 0.001, Student’s t-test).

Figure 2

Antiproliferative assay. The histograms show the antiproliferative effects of fractions C and D of C. closterium extracts, on A549, A2058, and HepG2 cell lines. Control sample, containing only DMSO, was also tested (named as control). Results are expressed as percent survival after 72 h exposure (n = 3).

Figure 3

Base peak intensity chromatograms of fraction A, B, C, and D from the UHPLC-HR-MS/MS analysis using positive electrospray.

Figure 4

Anti-inflammatory assay. Inhibition of TNF-α secretion from LPS-stimulated THP-1 cells treated with 3.13, 6.25, 12.5, 25, and 50 μg/mL of 1-Palmitoyl-sn-glycero-3-phosphocholine (n = 3; * for p < 0.05 and ** for p < 0.01, Student’s t-test).