Chlorophylls are the green pigments that absorb light for photosynthesis in plants, algae and photosynthetic bacteria. The molecule illustrated is chlorophyll a, the most abundant form in plants. Biochemists will recognize the basic square tetrapyrrole arrangement, which chlorophyll shares with haem (the chromophore in cytochromes and haemoglobin. Two features that distinguish chlorophylls are the magnesium (Mg)atom in the centre, and the lipophilic phytol tail (stretching up) that anchorschlorophylls in the photosynthetic membranes.

When chlorophyll is organised properly in the photosynthetic machinery, the light energy it harvests goes to productive use (or at least to harmless pathways). However, disorganised chlorophyll poses an ever-present danger as a powerful photosensitiser of oxidative damage [1]. Because of this property, chlorophylls and derivatives can be used in medicine to target cancers and pathogens [2].

When plants need to break down chlorophyll it is done quickly and efficiently, first taking off the phytol to produce #chlorophyllide, and then breaking down any dangerous intermediates. On cooking green vegetables (e.g. spinach), chlorophyll can lose the central magnesium to produce a dingy looking molecule called #pheophytin! Chlorophyll that has neither phytol nor Mg, is called #pheophorbide, worthy of mention because of interesting antiviral activity, notably against SARS-CoV-2, the#COVID-19 virus [3].

#Chlorophyllinis a semisynthetic a semisynthetic derivative with no phytol and with copperre placing magnesium in the central position. It is vivid green, stable and designated as food colour E141. It has been used in toothpaste, in cosmetics and ingestable products intended to reduce odour of urine and faeces. Notably, users of products that contain  chlorophyll derivatives are advised to minimise their exposure to the sun!

1.        Raskin, V.I., Marder,J.B.: How plants limit the photodestructive potential of chlorophyll. Currenttopics in plant physiology (USA). (1993)

2.        Brandis, A.S.,Salomon, Y., Scherz, A.: Chlorophyll Sensitizers in Photodynamic Therapy. Chlorophylls and Bacteriochlorophylls. 461–483 (2006).https://doi.org/10.1007/1-4020-4516-6_32

3.        Jimenez-Aleman, G.H.,Castro, V., Londaitsbehere, A., Gutierrez-Rodríguez, M., Garaigorta, U., Solano, R., Gastaminza, P.: SARS-CoV-2 Fears Green: The Chlorophyll Catabolite Pheophorbide A Is a Potent Antiviral. (2021).https://doi.org/10.3390/ph14101048

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