Petr Protiva

Bio: Petr Protiva is an academic researcher from City University of New York. The author has contributed to research in topics: DPPH & Biphenyl compound. The author has an hindex of 3, co-authored 3 publications receiving 344 citations. Previous affiliations of Petr Protiva include University of Miami.

Bioactive novel polyphenols from the fruit of Manilkara zapota (Sapodilla).

Abstract: Activity-guided fractionation of a methanol extract from the fruit of Manilkara zapota cv. Tikal resulted in the isolation of two new antioxidants, methyl 4-O-galloylchlorogenate (1) and 4-O-galloylchlorogenic acid (2), along with eight known polyphenolic antioxidants, namely, methyl chlorogenate (3), dihydromyricetin (4), quercitrin (5), myricitrin (6), (+)-catechin (7), (−)-epicatechin (8), (+)-gallocatechin (9), and gallic acid (10). Of the 10 polyphenols, 1 showed the highest antioxidant activity (IC50 = 12.9 μM) in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical assay and displayed cytotoxicity in the HCT-116 and SW-480 human colon cancer cell lines with IC50 values of 190 and 160 μM, respectively. Compound 2 showed high antioxidant activity (IC50 = 23.5 μM) in the DPPH free-radical assay and displayed cytotoxicity in the HCT-116 and SW-480 human colon cancer cell lines with IC50 values of 154 and 134 μM, respectively.

Bioactive Benzophenones from Garcinia xanthochymus Fruits

Abstract: A MeOH extract of Garcinia xanthochymus fruits was subjected to activity-guided fractionation, yielding two new benzophenones, guttiferone H (1) and gambogenone (2). Compound 1 contains a seven-membered ring attached to the bicyclo[3.3.1]nonane system at positions 7 and 8 and displayed cytotoxicity in the SW-480 colon cancer cell line (IC(50) = 12 microM). Compound 2 has a novel benzophenone bicyclo[3.3.2]decane system and displayed cytotoxicity in the SW-480 colon cancer cell line (IC(50) = 188 microM). Both 1 and 2 induced apoptosis in SW-480 colon cancer cells and displayed antioxidant activity in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay (IC(50) = 64 and 38.7 microM, respectively). The structures of 1 and 2 were established by 1D and 2D NMR data analysis. Eleven known compounds, aristophenone A, alloathyriol, amentoflavone, 3,8' '-biapigenin, cycloxanthochymol, (+/-)-fukugetin, (+/-)-fukugiside, guttiferone E, isoxanthochymol, (+/-)-volkensiflavone, and xanthochymol, were also obtained. The 11 known compounds were also tested against SW-480 colon cancer cells and in the DPPH assay.

New bioactive polyphenols from Theobroma grandiflorum ("cupuaçu").

Abstract: Activity-guided fractionation of Theobroma grandiflorum (“cupuacu”) seeds resulted in the identification of two new sulfated flavonoid glycosides, theograndins I (1) and II (2). In addition, nine k...

A review on the dietary flavonoid kaempferol.

Abstract: Epidemiological studies have revealed that a diet rich in plant-derived foods has a protective effect on human health. Identifying bioactive dietary constituents is an active area of scientific investigation that may lead to new drug discovery. Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is a flavonoid found in many edible plants (e.g. tea, broccoli, cabbage, kale, beans, endive, leek, tomato, strawberries and grapes) and in plants or botanical products commonly used in traditional medicine (e.g. Ginkgo biloba, Tilia spp, Equisetum spp, Moringa oleifera, Sophora japonica and propolis). Some epidemiological studies have found a positive association between the consumption of foods containing kaempferol and a reduced risk of developing several disorders such as cancer and cardiovascular diseases. Numerous preclinical studies have shown that kaempferol and some glycosides of kaempferol have a wide range of pharmacological activities, including antioxidant, anti-inflammatory, antimicrobial, anticancer, cardioprotective, neuroprotective, antidiabetic, anti-osteoporotic, estrogenic/antiestrogenic, anxiolytic, analgesic and antiallergic activities. In this article, the distribution of kaempferol in the plant kingdom and its pharmacological properties are reviewed. The pharmacokinetics (e.g. oral bioavailability, metabolism, plasma levels) and safety of kaempferol are also analyzed. This information may help understand the health benefits of kaempferol-containing plants and may contribute to develop this flavonoid as a possible agent for the prevention and treatment of some diseases.

Gallic acid: a versatile antioxidant with promising therapeutic and industrial applications

Abstract: Oxidative stress, a result of an overproduction and accumulation of free radicals, is the leading cause of several degenerative diseases such as cancer, atherosclerosis, cardiovascular diseases, ageing and inflammatory diseases. Polyphenols form an important class of naturally occurring antioxidants, having innumerable biological activities such as anticancer, antifungal, antibacterial, antiviral, antiulcer and anticholesterol, to name a few. Among various polyphenols, gallic acid (3,4,5-trihydroxybenzoic acid), a naturally occurring low molecular weight triphenolic compound, has emerged as a strong antioxidant and an efficient apoptosis inducing agent. Starting from the bioavailability and the biosynthetic pathway of gallic acid, this review includes various in vitro, in vivo and in silico studies providing the mode of action, radical scavenging activity, ability to inhibit lipid peroxidation, maintenance of endogenous defense systems and metal ion chelation by this triphenolic molecule, along with a comprehensive overview of factors responsible for its high antioxidant activity. Gallic acid derivatives have also been found in a number of phytomedicines with diverse biological and pharmacological activities, including radical scavenging, interfering with the cell signaling pathways and apoptosis of cancer cells. The diverse range of applications of this simple polyphenol is due to a fine amalgam between its antioxidant and prooxidant potential. The existing literature on this dual behavior of gallic acid and its derivatives is reviewed here. This is followed by an account of their potential clinical and industrial applications.

Protein lysine acetylation by p300/CBP.

Abstract: Since their discovery in the 1980s and 1990s, the human protein lysine acetyltransferase encoded by the paralogous p300 and CBP genes has received much interest. p300/CBP functions in regulating the expression of genes controlling several basic cellular processes, such as proliferation and homeostasis, and plays a role in a variety of human diseases, particularly solid tumors. Numerous natural product and synthetic inhibitors of the acetyltransferase activity have been identified and used to generate a crystal structure of the active site, probe the p300/CBP enzyme kinetics, and interrogate p300/CBP cellular functions. These studies revealed that acetyl-CoA binds in a tunnel enclosed by a unique loop, while the substrate protein transiently associates with an acidic patch, following a hit-and-run kinetic mechanism. p300/CBP acetylates histones as well as other proteins including other epigenetic enzymes and transcription factors. Studies with inhibitor compounds in cells and animals have confirmed that the p300/CBP acetylation activity has roles in diverse functions including cell migration and invasion, maintenance of the differentiated state, tau-mediated neurodegeneration, and learning and memory. Also, important components of p300/CBP are the domains flanking the acetyltransferase domain, including three cysteine/histidine-rich domains and a bromodomain. Protein ligands of these have been identified. Their roles in regulating the acetyltransferase activity and substrate specificity, as well as identification of compounds that can block or mimic ligand binding, are topics of ongoing study. Biochemical investigation of protein acetylation has posed unique challenges, due in part to its dynamic reversibility, the weak affinity of binding modules that recognize it, and the complexity of the multiprotein interaction networks. Therefore, diverse techniques in biochemistry, molecular biology, and proteomics have coevolved with our understanding of the p300/CBP enzyme. In this Review, part of the thematic issue on Epigenetics, we summarize the current understanding of p300/CBP including the novel technologies developed for these studies.

Total Antioxidant Activity and Fiber Content of Select Florida-Grown Tropical Fruits

Abstract: Fourteen tropical fruits from south Florida (red guava, white guava, carambola, red pitaya (red dragon), white pitaya (white dragon), mamey sapote, sapodilla, lychee, longan, green mango, ripe mango, green papaya, and ripe papaya) were evaluated for antioxidant activity, total soluble phenolics (TSP), total ascorbic acid (TAA), total dietary fiber (TDF), and pectin. ORAC (oxygen radical absorbance capacity) and DPPH (1,1-diphenyl-2-picrylhydrazyl, radical scavenging activity) assays were used to determine antioxidant activity. The TSP, ORAC, and DPPH ranged from 205.4 to 2316.7 g gallic acid equiv/g puree, <0.1 to 16.7 Imol Trolox equiv/g puree, and 2.1 to 620.2 Ig gallic acid equiv/g puree, respectively. The TAA, TDF, and pectin ranged from 7.5 to 188.8 mg/100 g, 0.9 to 7.2 g/100 g, and 0.20 to 1.04 g/100 g, respectively. The antioxidant activities, TSP, TAA, TDF, and pectin were influenced by cultivar (papaya, guava, and dragon fruit) and ripening stage (papaya and/or mango). Antioxidant activity showed high correlations with levels of TSP compounds (r ) 0.96) but low correlations with levels of ascorbic acid (r ) 0.35 and 0.23 for ORAC and DPPH data, respectively). The antioxidant activities evaluated by both ORAC and DPPH showed similar trends where red guava and carambola exhibited the highest and sapodilla and green papaya exhibited the lowest levels. Guava and mamey sapote exhibited the highest TDF and pectin levels. Many of the tropical fruits were shown to contain an abundance of hydrolyzable tannins, ellagic acid conjugates, and flavone glycosides. Preliminary descriptions are given of the phenols in red/white pitaya (dragonfruit), lychee, and mamey sapote, these fruit being thus far uncharacterized in the literature.