Antioxidant Activity of Natural Hydroquinones

Abstract

Secondary metabolites derived from hydroquinone are quite rare in nature despite the original simplicity of its structure, especially when compared to other derivatives with which it shares biosynthetic pathways. However, its presence in a prenylated form is somewhat relevant, especially in the marine environment, where it is found in different algae and invertebrates. Sometimes, more complex molecules have also been identified, as in the case of polycyclic diterpenes, such as those possessing an abietane skeleton. In every case, the presence of the dihydroxy group in the para position gives them antioxidant capacity, through its transformation into para-quinones.This review focuses on natural hydroquinones with antioxidant properties referenced in the last fifteen years. This activity, which has been generally demonstrated in vitro, should lead to relevant pharmacological properties, through its interaction with enzymes, transcription factors and other proteins, which may be particularly relevant for the prevention of degenerative diseases of the central nervous system, or also in cancer and metabolic or immune diseases. As a conclusion, this review has updated the pharmacological potential of hydroquinone derivatives, despite the fact that only a small number of molecules are known as active principles in established medicinal plants. The highlights of the present review are as follows: (a) sesquiterpenoid zonarol and analogs, whose activity is based on the stimulation of the Nrf2/ARE pathway, have a neuroprotective effect; (b) the research on pestalotioquinol and analogs (aromatic ene-ynes) in the pharmacology of atherosclerosis is of great value, due to their agonistic interaction with LXRα; and (c) prenylhydroquinones with a selective effect on tyrosine nitration or protein carbonylation may be of interest in the control of post-translational protein modifications, which usually appear in chronic inflammatory diseases.

Keywords: alkyl phenolics; antioxidant; hydroquinones; marine natural products; meroterpenoids; reactive oxygen species; secondary metabolites.

Figure 1

Chemical structures of hydroquinone (a) and arbutin (b).

Figure 2

Chemical structure of benzyl 5-O-β-D-glucopyranosyl-2,5-dihydroxybenzoate isolated from Mikania micrantha.

Figure 3

Chemical structure of 4-hydroxyphenyl-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside isolated from Triticum aestivum.

Figure 4

Chemical structure of robustaside B isolated from Cnestis ferruginea.

Figure 5

Chemical structures of hydroquinones isolated from Origanum majorana.

Figure 6

Chemical structures of hydroquinones isolated from Piper crassinervium.

Figure 7

Chemical structures of the new hydroquinones isolated from Cystoseiracrinita.

Figure 8

Chemical structures of hydroquinones and closely related derivatives isolated from Dictyopteris undulata.

Figure 9

Chemical structures of hydroquinones isolated from Sarcotragus muscarum.

Figure 10

Chemical structures of hydroquinones and related compounds isolated from Sargassum micracanthum.

Figure 11

Chemical structures of hydroquinones isolated from Ganoderma capense.

Figure 12

Chemical structure of zinolol isolated from Anagallis monelli.

Figure 13

Chemical structures of hydroquinones isolated from Rhus succedanea.

Figure 14

Chemical structure of phlebotrichin from Viburnum erosum.

Figure 15

Chemical structure of pestalotioquinol C (a) and pestalotioquinoside C (b) isolated from a fermentation broth of Pestalotiopsis neglecta, a fungus endophytic to Coelarthrum sp.

Figure 16

Chemical structures of hydroquinones isolated from Ganoderma theaecolum.

Figure 17

Chemical structures of hydroquinones isolated from Ganoderma lucidum.

Figure 18

Chemical structures of cryptoquinone (a), isolated from Cryptomeria japonica, and of the synthetic hydroquinone, 11,14-dihydroxy-8,11,13-abietatriene (b).

Figure 19

Chemical structure of strongylophorine-8, isolated from Petrosia corticata.

Figure 20

Chemical structures of hydroquinones isolated from Pestalotiopsis microspora.

Figure 21

Chemical structures of hydroquinones isolated from Amaroucium multiplicatum.

Figure 22

Chemical structures of hydroquinones isolated from Phagnalon rupestre.