Naringenin is one of the most abundant dietary flavonoids exerting several beneficial biological activities. Synthetic modification of naringenin is of continuous interest. During this study our aim was to synthesize a compound library of oxime and oxime ether derivatives of naringenin, and to investigate their biological activities. Two oximes and five oxime ether derivatives were prepared; their structure has been elucidated by NMR and high-resolution mass spectroscopy. The antiproliferative activity of the prepared compounds was evaluated by MTT assay against human leukemia (HL-60) and gynecological cancer cell lines isolated from cervical (HeLa, Siha) and breast (MCF-7, MDA-MB-231) cancers. Tert-butyl oxime ether derivative exerted the most potent cell growth inhibitory activity. Moreover, cell cycle analysis suggested that this derivative caused a significant increase in the hypodiploid (subG1) phase and induced apoptosis in Hela and Siha cells, and induced cell cycle arrest at G2/M phase in MCF-7 cells. The proapoptotic potential of the selected compound was confirmed by the activation of caspase-3. Antioxidant activities of the prepared molecules were also evaluated with xanthine oxidase, DPPH and ORAC assays, and the methyl substituted oxime ether exerted the most promising activity.

Cancer cells generally possess higher levels of reactive oxygen species than normal cells, and this can serve as a possible therapeutic target. In this proof-of-concept study, an antioxidant-inspired drug discovery strategy was evaluated using a hydroxycinnamic acid derivative. The processing of oxidized mixtures of p-coumaric acid methyl ester (pcm) revealed a new antitumor lead, graviquinone. Graviquinone bypassed ABCB1-mediated resistance, induced DNA damage in lung carcinoma cells but exerted DNA protective activity in normal keratinocytes, and modulated DNA damage response in MCF-7 cells. The cytotoxic effect of pcm in MCF-7 cells was potentiated under H2O2-induced oxidative stress, and the formation of graviquinone was confirmed by Fenton’s reaction on pcm. In silico DFT calculations suggested graviquinone as a kinetic product of pcm scavenging •OH radicals. Our results demonstrate the pharmacological value of an in situ-formed, oxidative stress-related metabolite of an antioxidant. This might be of particular importance for designing new strategies for antioxidant-based drug discovery.

Resveratrol is a well-known natural polyphenol with a plethora of pharmacological activities. As a potent antioxidant, resveratrol is highly oxidizable and readily reacts with reactive oxygen species (ROS). Such a reaction not only leads to a decrease in ROS levels in a biological environment but may also generate a wide range of metabolites with altered bioactivities. Inspired by this notion, in the current study, our aim was to take a diversity-oriented chemical approach to study the chemical space of oxidized resveratrol metabolites. Chemical oxidation of resveratrol and a bioactivity-guided isolation strategy using xanthine oxidase (XO) and radical scavenging activities led to the isolation of a diverse group of compounds, including a chlorine-substituted compound (2), two iodine-substituted compounds (3 and 4), two viniferins (5 and 6), an ethoxy-substituted compound (7), and two ethoxy-substitute,0d dimers (8 and 9). Compounds 4, 7, 8, and 9 are reported here for the first time. All compounds without ethoxy substitution exerted stronger XO inhibition than their parent compound, resveratrol. By enzyme kinetic and in silico docking studies, compounds 2 and 4 were identified as potent competitive inhibitors of the enzyme, while compound 3 and the viniferins acted as mixed-type inhibitors. Further, compounds 2 and 9 had better DPPH scavenging activity and oxygen radical absorbing capacity than resveratrol. Our results suggest that the antioxidant activity of resveratrol is modulated by the effect of a cascade of chemically stable oxidized metabolites, several of which have significantly altered target specificity as compared to their parent compound.

According to modern ethnobotanical records, the fruit of Hippophae rhamnoides is effective in the treatment of different allergic symptoms. In order to obtain pharmacological evidence for this observation, the fruit was investigated for anti-inflammatory activity using in vivo animal models. Aqueous and 70% MeOH extracts were tested in 48/80-induced rat paw edema assay after oral administration, and it was found that the 70% MeOH extract (500 mg/kg) reduced significantly edema volume (0.660 ± 0.082 mL vs. control 0.935 ± 0.041 mL). Extracts of different parts of the fruit (pulp, peel, seed) were investigated in the same assay, and the peel extract was shown to exhibit maximum edema-reducing effect (0.470 ± 0.124 mL vs. control 0.920 ± 0.111 mL). This extract was used to elucidate the mode of action. Different inflammation inducers (serotonin, histamine, dextran, bradykinin, and carrageenan) were applied in the rat paw model, but the extract inhibited only the compound 48/80 elicited inflammation. The active extract was then fractionated by solvent-solvent partitioning and chromatographic methods with the guidance of the 48/80-induced anti-inflammatory assay, and the main compounds responsible for the activity were identified as ursolic acid and oleanolic acid. Our data suggest that the activity is most probably based on a membrane stabilizing effect caused by the inhibition of degranulation of mast cells. Moreover, previously unknown 2,5-bis-aryl-3,4-dimethyltetrahydrofuran lignans, nectandrin B, fragransin A₂, and saucernetindiol were isolated and identified from H. rhamnoides for the first time.

Context: Rhodiola rosea L. (Crassulaceae) is well-known to contain flavonoids such as the herbacetin derivative rhodiosin. However, flavonoids are not typically used in quality control. Objective: This study analyses two flavonoids of R. rosea rhizomes and roots for their potential as analytical markers. Materials and methods: Two constituents were isolated from ethanolic extracts via HPLC, identified via NMR and quantified via RP-HPLC. Presence and content variation was investigated according to extraction (solvent and repetitions), drying (temperature and duration) and sample origin (homogenously cultivated plants of different provenance, commercial samples). Results: Rhodiosin was identified as a main flavonoid, accompanied by 10-fold lower concentrated herbacetin. Both compounds were best extracted with 70–90% ethanol, but were also detectable in more aqueous extracts. Different drying conditions had no effect on the flavonoid content. These two flavonoids were consistently identified in rhizome and root extracts of over 100 R. rosea samples. Rhizomes tend to contain less flavonoids, with average ratios of rosavins to flavonoids of 1.4 (rhizomes) and 0.4 (roots). Provenance differences were detected in the range (rhodiosin plus herbacetin) of 760–6300 µg/mL extract corresponding to a maximum of approximately 0.5–4.2% (w/w) in the dry drug. Conclusions: For the first time, two main flavonoids present in R. rosea were quantified systematically. Rhodiosin and herbacetin can be detected simultaneously to phenylpropenoids or salidroside in authentic samples, influenced by the plant part examined and the plant origin. Rhodiosin and herbacetin may serve as additional marker to guarantee a consistent content of R. rosea products.

Black mulberry is a widely acknowledged ancient traditional medicine. Its extract and constituents have been reported to exert various bioactivities including antimicrobial, hypotensive, analgesic etc. effects. While black mulberry preparations are also used as antispasmodic agents in folk medicine, no related studies are available on its isolated constituents. Through an extensive chromatographic purification, seven phenolic compounds were isolated from the methanol extract of Morus nigra root bark, including morusin (1), kuwanon U (2), kuwanon E (3), moracin P (4), moracin O (5), albanol A (6), and albanol B (7). A complete NMR signal assignment of moracin P and O was achieved, and related literature errors confusing the identity of moracin derivatives are hereby clarified. Compounds 2, 5 and 7 were identified as strong antispasmodic agents on isolated rat ileum and tracheal smooth muscles, while compound 3, a methoxy derivative of 2, was inactive. Moracin O (5) inhibited the ileal and tracheal smooth muscle contractions with E_max values of 85% and 302 mg, respectively. Those actions were superior as compared with papaverine. Our findings demonstrate that prenylated arylbenzofurans, geranylated flavonoids and Diels-Alder adducts from Morus nigra are valuable antispasmodic agents. Compounds 2, 5 and 7 are suggested as marker compounds for quality control of antispasmodic mulberry preparations. Moracin O (5) is a new lead compound for related drug development initiatives.