HPTLC Autography Based Screening and Isolation of Mushroom Tyrosinase Inhibitors of European Plant Species

Abstract

In the course of this project, 133 plants were evaluated on their ability to inhibit tyrosinase, a key enzyme in melanogenesis. The screening was performed by means of a HPTLC autographic assay, resulting in the selection of three plants, Asplenium trichomanes, Pinus uncinata, and Scutellaria altissima, with promising tyrosinase inhibiting activities. With the aid of the HPTLC assay, it was not only possible to select the most interesting plant extracts, but also to monitor the activity‐guided fractionation which, in a relatively short time period, led to the isolation of active principles. Benzoic acid, roseoside, and dihydrovomifoliol‐O‐β‐d‐glucopyranoside could be identified as tyrosinase inhibitors present in P. uncinata. Globularin turned out to be the active principle of S. altissima, and 4‐ethenylphenyl 6‐O‐(6‐deoxy‐α‐l‐mannopyranosyl)‐β‐d‐glucopyranoside was detected as tyrosinase inhibitor of A. trichomanes. The pure compounds were tested also in a 96 well‐plate assay in order to determine their IC50 values. The lowest IC50 value (42 μm) could be obtained for globularin, whereas the other compounds, e. g., benzoic acid exhibited a rather high IC50 value (IC50=552 μm). This stood in clear contrast to the autographic assay, but is has to be taken into account that the outcome of the autography assay is not only depending on the IC50 value of a compound, but also on the content of the respective constituent in the extract.

Diverting phenylpropanoid pathway flux from sinapine to produce industrially useful 4-vinyl derivatives of hydroxycinnamic acids in Brassicaceous oilseeds

“…4-VP diglucoside, 4VP rhamnosyl glucopyranoside and 4-VP apiofuranosyl glucopyranoside). Of these, 4-VP rhamnosyl glucoside is the most abundant styrene analogue we observed, an arrangement previously reported in other styrene analogues identified in bracken fern ( Pteridium aquilinum ) and maidenhair spleenwort ( Asplenium trichomanes ) ( Ojika et al, 1987 ; Revoltella et al, 2019 ). Phenolic compounds are frequently glycosylated in plants ( Le Roy et al, 2016 ) and pathway manipulation can lead to the production of new glycosides that are formed by the activities of native UTP-glycosyltransferases (UGTs).…”

“…4-VP glycosides have previously been detected in ferns ( Ojika et al, 1987 ; Revoltella et al, 2019 ). However, they have not been reported previously in angiosperms (to our knowledge) and we show that 4-VP (and other vinyl derivatives of hydroxycinnamic acids such as 4-VS) can be made in angiosperms using metabolic engineering.…”

“…To our knowledge, 4-VS is the only vinyl derivative of a 4-hydroxycinnamic acid that has previously been reported in angiosperms, where low levels (>50 μg g -1 ) are found in rapeseed and are presumed to be the product of spontaneous thermal decarboxylation of sinapine ( Matthäus et al, 2014 ; Wakamatsu et al, 2005 ). 4-VP glucosides have also been detected in the ferns Pteridium aquilinum and Asplenium trichomanes ( Ojika et al, 1987 ; Revoltella et al, 2019 ).…”

Design, synthesis, in vitro and in silico studies of novel Schiff base derivatives of 2‐hydroxy‐4‐methoxybenzamide as tyrosinase inhibitors

“…Literature survey highlighted natural and synthetic TYRIs including terpenoids (Ashraf et al, 2017;Lehbili et al, 2018;Revoltella et al, 2019) chalcones, hydrochalcones (Huang et al, 2010;Niesen et al, 2015;Takahashi et al, 2012), oxadiazole, triazolothiadiazole (Ghani & Ullah, 2010;Ha et al, 2012;Lam et al, 2010), thiosemicarbazone (Lee et al, 2010;Yi et al, 2011) derivatives.…”

A novel study approach on Scutellaria altissima L. cultivated at the Ghirardi Botanic Garden (Lombardy, Italy)

“…Referring to the biological activity, studies on EO are lacking. However, the antioxidant action of the ethanol extract of aerial parts and roots is known (Grzegorczyk‐Karolak et al, 2019), together with the inhibitory effect of the methanol extract on the tyrosinase enzyme (Revoltella et al, 2019) and the antifeedant, cytotoxic, chemo‐sensitizing and neuroprotective properties of some molecules isolated from the plant (Bozov & Georgieva, 2017; Gao et al, 2017; Jia et al, 2019). In addition, S. scordifolia L. methanolic extracts, obtained at room temperature, showed activity against Candida spp., Malassezia furfur and other dermatophytes (Giordani et al, 2020).…”