nally high quantity of accumulated dihydrochalcones [11], gave rise to speculation concerning the physiological SIRT2 Formulation function of dihydrochalcones in thisCopyright: 2021 by the authors. Licensee MDPI, Basel, Switzerland. This short article is an open access write-up distributed below the terms and situations in the Creative Commons Attribution (CC BY) license ( creativecommons.org/licenses/by/ four.0/).Plants 2021, 10, 1956. doi.org/10.3390/plantsmdpi/journal/plantsPlants 2021, ten, x FOR PEER REVIEWPlants 2021, 10,two of2 of[70]. The unique case of apple, with its exceptionally high volume of accumulated dihydrochalcones [11], gave rise to speculation regarding the physiological function of dihydrochalcones A function in pathogen defense was controversiallycontroversially discussedsystemspecies. within this species. A function in pathogen defense was discussed [1,124]. For [1,1214]. For systematic investigation, sufficiently complete expertise of your underlyatic investigation, sufficiently complete information from the underlying pathway is ing pathway is still lacking. nevertheless lacking.R3OHHO4OH2ROFigure 1. Chemical structures of chosen dihydroxychalcones found in Malus species. R=H, R’=OH: Figure 1. Chemical structures of chosen dihydroxychalcones found in Malus species. R=H, R’=OH: Phloretin. R’=OH: 3-Hydroxyphloretin. R=H, R’=Glc: Phloretin two -O-glucoside (phloridzin). Phloretin. R,R, R’=OH: 3-Hydroxyphloretin.R=H, R’=Glc: Phloretin 2-O-glucoside (phloridzin). R=OH, R’=Glc: 3-Hydroxyphloretin 2 -O-glucoside (3-hydroxyphloridzin). R=OH, R’=Glc: 3-Hydroxyphloretin 2-O-glucoside (3-hydroxyphloridzin).3-Hydroxyphloridzin, carrying further hydroxyl group at at position inside the 3-Hydroxyphloridzin, carrying anan further hydroxyl group position three in3the BB-ring (Figure 1), is also present constitutively, even though in incredibly low amounts [1]. Using ring (Figure 1), can also be present constitutively, though in very low amounts [1]. Using transtransgenic M. domestica plants, we previously showed that an increase in 3-hydroxylated genic M. domestica plants, we previously showed that a rise in 3-hydroxylated didihydrochalcones correlates having a lower susceptibility for fire blight and apple scab [15]. 3hydrochalcones correlates with a reduce susceptibility for fire blight and apple scab [15]. Hydroxyphloridzin and 3-hydroxyphloretin can take place as VEGFR1/Flt-1 Biological Activity intermediates within the oxidation of 3-Hydroxyphloridzin and 3-hydroxyphloretin can take place as intermediates in the oxidation phloridzin and phloretin by polyphenol oxidases (PPO). Not too long ago, 3 recombinant PPOs of phloridzin and phloretin by polyphenol oxidases (PPO). Lately, three recombinant from M. domestica were characterized with tyramine and dopamine as substrates and PPOs from M. domestica have been characterized with tyramine and dopamine as substrates classified as tyrosinases [16,17]. The recommended involvement of PPOS [18,19] is specifically and classified as tyrosinases [16,17]. The recommended involvement of PPOS [18,19] is particquestionable as in intact cells, PPOs and dihydrochalcones, as with polpyhenols normally, ularly questionable as in intact cells, PPOs and dihydrochalcones, as with polpyhenols in are believed to be kept in separate cell compartments to prevent undirected cell damage basic, are thought to become kept in separate cell compartments to prevent undirected cell by interaction with quinones, that are the final merchandise of polyphenol oxidation by damage by interaction with quinones, that are the final goods of p