Characterizing some photophysical, photochemical and photobiological properties of photosensitizing anthraquinones

Reduction ofCandida tropicalisbiofilm by photoactivation of aHeterophyllaea pustulataextract

“…Thus, the significant antifungal activity of the Ben extract, observed under irradiation (Figure 2), can be attributed to its high content of AQs with photosensitizing properties, since we have established that this effect was due to a high ROS production (Figure 4). It is important to highlight that the rubiadin (1) and soranjidiol (2) were the predominant AQs in this extract, which have shown to be good photosensitizers by stimulating the O 2 •À generation (Type I) (Nuñez Montoya et al 2005;Comini et al 2007), and this ROS is the main precursor of other oxygen species highly reactive like H 2 O 2 and hydroxyl radical (OH • ). On the other hand, the low-mid concentration of photosensitizing AQs in the Hex, EtOAc and EtOH extracts (Table 5), along with the presence of significant amounts of flavonoids with proven antioxidant properties as quercetin (10) and isoquercitrin (11) (Permana et al 2003;Boots et al 2008) in the polar extracts (EtOAc and EtOH), would be the cause for a lowmid ROS production by these three extracts, and consequently of their inactivity against biofilm.…”

“…By applying this validated HPLC method, we established that the AQs with photosensitizing properties (Nuñez Montoya et al 2005;Comini et al 2007) would be responsible for the effect produced by Ben extract, since only this extract contains exclusively photosensitizing AQs in high concentrations and was the only one that exhibited a significant lowering effect over the biofilm growth by light action. In the case of Hex extract, AQs concentration was lower than in the Ben extract, and would seem that the activation of the total antioxidant system would counteract the effect of the few ROS and RNI generated by the AQs present in this extract.…”

“…The chemical investigation of bioactive extracts revealed the predominance of 9,10-anthraquinone aglycones (AQs) (Figure 1) (Nuñez Montoya et al 2003, 2006Konigheim et al 2012) with demonstrated photosensitizing properties, which act by Type I (superoxide anion radical production, O 2 •À ) and/or Type II (singlet oxygen generation, 1 O 2 ) mechanisms (Nuñez Montoya et al 2005;Comini et al 2007). …”

Ultrasonic-assisted extraction of anthraquinones from Heterophyllaea pustulata Hook f. (Rubiaceae) using ethanol–water mixtures

“…Thus, from the aerial parts of H. pustulata three flavonoids (quercetin, isoquercitrin, quercetin-3-O-␣-D-glucosyl-6"-acetate), an glicosyde iridoid (asperuloside), ten aglycone-AQs: soranjidiol, soranjidiol 1-methyl ether, rubiadin, rubiadin 1-methyl ether, damnacanthal, damnacanthol, heterophylline, pustuline, 5,5-bisoranjidiol, and 2-hydroxi-3-methyl anthraquinone were isolated. The first nine AQs have photosensitizing properties, mediated by the generation of superoxide anion (O 2 .− ; type I mechanism) and/or singlet molecular oxygen ( 1 O 2 ; type II mechanism) (Núñez Montoya et al, 2005;Comini et al, 2007). Three of these AQs, soranjidiol, rubiadin and 1-methyl ether rubiadin, stand out as the main components of leaves and stems (Nuñez Montoya et al, 2003).…”

Direct and ketone-sensitized photoconversion of 1-nitro-9,10-anthraquinone to 1-amino-9,10-anthraquinone mediated by donor radicals

“…The photochemical features of 9,10-anthraquinone (AQ) and several derivatives in solution have been intensively studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The key-intermediate in the photoreduction of AQs is the semiquinone radical, the properties of which have been reviewed [17].…”