The dietary flavonoids, especially their glycosides, are the most vital phytochemicals in diets and are of great general interest due to their diverse bioactivity. The natural flavonoids almost all exist as their O-glycoside or C-glycoside forms in plants. In this review, we summarized the existing knowledge on the different biological benefits and pharmacokinetic behaviors between flavonoid aglycones and their glycosides. Due to various conclusions from different flavonoid types and health/disease conditions, it is very difficult to draw general or universally applicable comments regarding the impact of glycosylation on the biological benefits of flavonoids. It seems as though O-glycosylation generally reduces the bioactivity of these compounds - this has been observed for diverse properties including antioxidant activity, antidiabetes activity, anti-inflammation activity, antibacterial, antifungal activity, antitumor activity, anticoagulant activity, antiplatelet activity, antidegranulating activity, antitrypanosomal activity, influenza virus neuraminidase inhibition, aldehyde oxidase inhibition, immunomodulatory, and antitubercular activity. However, O-glycosylation can enhance certain types of biological benefits including anti-HIV activity, tyrosinase inhibition, antirotavirus activity, antistress activity, antiobesity activity, anticholinesterase potential, antiadipogenic activity, and antiallergic activity. However, there is a lack of data for most flavonoids, and their structures vary widely. There is also a profound lack of data on the impact of C-glycosylation on flavonoid biological benefits, although it has been demonstrated that in at least some cases C-glycosylation has positive effects on properties that may be useful in human healthcare such as antioxidant and antidiabetes activity. Furthermore, there is a lack of in vivo data that would make it possible to make broad generalizations concerning the influence of glycosylation on the benefits of flavonoids for human health. It is possible that the effects of glycosylation on flavonoid bioactivity in vitro may differ from that seen in vivo. With in vivo (oral) treatment, flavonoid glycosides showed similar or even higher antidiabetes, anti-inflammatory, antidegranulating, antistress, and antiallergic activity than their flavonoid aglycones. Flavonoid glycosides keep higher plasma levels and have a longer mean residence time than those of aglycones. We should pay more attention to in vivo benefits of flavonoid glycosides, especially C-glycosides.

Dietary flavonoid aglycones and their glycosides: Which show better biological significance?

Advances in the biotechnological glycosylation of valuable flavonoids

Lipoxygenases (LOXs) are non-heme iron containing dioxygenases involved in the oxygenation of polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA). Depending on the position of insertion of oxygen, LOXs are classified into 5-, 8-, 9-, 12- and 15-LOX. Among these, 5-LOX is the most predominant isoform associated with the formation of 5-hydroperoxyeicosatetraenoic acid (5- HpETE), the precursor of non-peptido (LTB4) and peptido (LTC4, LTD4, and LTE4) leukotrienes. LTs are involved in inflammatory and allergic diseases like asthma, ulcerative colitis, rhinitis and also in cancer. Consequently 5-LOX has become target for the development of therapeutic molecules for treatment of various inflammatory disorders. Zileuton is one such inhibitor of 5-LOX approved for the treatment of asthma. In the recent times, computer aided drug design (CADD) strategies have been applied successfully in drug development processes. A comprehensive review on structure based drug design strategies in the development of novel 5-LOX inhibitors is presented in this article. Since the crystal structure of 5-LOX has been recently solved, efforts to develop 5-LOX inhibitors have mostly relied on ligand based rational approaches. The present review provides a comprehensive survey on these strategies in the development of 5-LOX inhibitors.

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Structure and Ligand Based Drug Design Strategies in the Development of Novel 5-LOX Inhibitors

Novel imidazo[2,1-b][1,3,4]thiadiazole carrying rhodanine-3-acetic acid as potential antitubercular agents

Synthesis, antioxidant activity, and quantitative structure–activity relationship (QSAR) of 25 of chalcone derivatives is reported here. They were synthesized by Claisen–Schmidt reaction and were characterized by FTIR, NMR, and mass spectroscopy. Antioxidant activity is evaluated through four different methods namely, superoxide radical-scavenging, hydrogen peroxide scavenging, reducing power, and DPPH radical-scavenging assays. Generally, compounds with –SCH3 and –OCH3 in the para position of the A-ring and –OH in the B-ring were more active than others. In few cases some of the compounds were more active than ascorbic acid or butylated hydroxytoluene. QSAR was developed correlating the antioxidant activity with the structural features of the compounds and the predictive capability of the models was estimated using internal and external validation methods. All the predictions were within the 99% confidence level. Spatial, structural, and lipophilic properties of the compounds determine their antioxidant properties.

Synthesis, antioxidant evaluation, and quantitative structure–activity relationship studies of chalcones

Design of compounds having good anti-tubercular activity is gaining much importance in the field of tuberculosis research due to reemergence of antibiotic resistance strains. In this paper quantitative structure activity relationships (QSAR) were developed on chalcones, chalcone-like compounds, flavones and flavanones to understand the relationship between biological activity and structural features. Genetic function approximation (GFA) method was used to identify the descriptors that would lead to good regression equations. The best molecular descriptors identified were Jurs descriptors (Jurs charged partial surface area), hydrogen bond donor, principal moment of inertia, molecular energy, dipole magnetic, molecular area, absorption, distribution, metabolism and excretion (ADME) properties and Chi indices (Kier & Hall chi connectivity indices). Excellent statistically significant models were developed by this approach (r(2)=0.8-0.97) for the four groups of compounds. The cross validated r(2) (XV r(2)) which is an indication of the predictive capability of the model for all the cases was also very good (=0.79-0.94).

QSAR Studies on chalcones and flavonoids as anti-tuberculosis agents using genetic function approximation (GFA) method

Quantitative structure activity relationships (QSAR) were developed relating the 14th and 21st day antituberculosis activity against H(37)Rv strain of Mycobacterium tuberculi and antibacterial activity against Staphylococcus aureus ATCC3750, Bacillus subtilis 6633, Escherichia coli ATCC3750, and Salmonella typhi NCTC786 of 55 pyrazine containing thiazolines and thiazolidinones, with the molecular descriptors. The developed models were able to fit the data well (r(2) = 0.69-0.87) and had reasonable predictive capability (q(2) > 0.62). The data were also divided into a training set and a test set, the former was used to develop the QSAR and the latter was used to evaluate the predictive capability of these developed models. In all the cases, the models were able to predict the test data set reasonably well. Predominantly, pyrazine ring is well-known for its antimycobacterial activity and hence these equation could be used to design newer analogues with higher activity. These compounds also possess both antitubercular and antibacterial activity. Descriptors pertaining to electronic, topology, and hydrophobicity of the molecules appear in the model equations.

Impact of Topological and Electronic Descriptors in the QSAR of Pyrazine Containing Thiazolines and Thiazolidinones as Antitubercular and Antibacterial Agents

QSAR and Docking Studies on Propenone Derivatives as Dual COX and 5- LOX Inhibitors

Background and Aim: The clinical assessments using the Child-Turcotte-Pugh (CTP) and model for end-stage liver disease-sodium (MELD-Na) scores are heterogeneous. The present study aims to collate most relevant markers of chronic liver disease as a new score BICEPS (Bilirubin, INR, Creatinine, Encephalopathy, Platelet and Sodium) an alternate to CTP and MELD-Na in patients diagnosed with liver cirrhosis. Methods: From January 2019 till December 2021, patients who were admitted with a diagnosis of liver cirrhosis were included. Patients were classified as per the CTP, MELD-Na and BICEPS scoring systems using a proforma. The BICEPS score is created by the authors and study intended to validate clinically. Results: In 211 patients, were evaluated during the study period including COVID pandemic period. The mean MELD-Na score was 23.49 ± 8.42, ranging 7 to 42, while CTP score ranged from 5 to 15, with a mean value of 9.65 ± 2.76. We classified patients as per scoring to 16%, 32% and 52% as Grade A, B and C on CTP respectively and 6%, 54% and 40% as Grade A, B and C on BICEPS respectively. We observed moderate level of agreement between BICEPS and CTP [Cohen’s kappa = 0.57, 95% confidence interval (CI) 0.45 to 0.69, p value < 0.01]. BICEPS correlated strongly with both MELD-Na [Pearson’s correlation coefficient (r) = 0.84, p value < 0.01] and CTP (r = 0.83, p value < 0.01). Conclusions: BICEPS yet another clinical scoring that has a moderate level of agreement with CTP and significant correlation with both CTP and MELD Na. Being a clinical scoring helps bedside estimation easy and includes all the 6 critical markers of CLD and is comparable to MELD Na without a calculator. Further studies are required with more number of patients for validating the BICEPS score. 

Sethu Kailasam Geetha Babu

Papers

QSAR Studies on chalcones and flavonoids as anti-tuberculosis agents using genetic function approximation (GFA) method

Impact of Topological and Electronic Descriptors in the QSAR of Pyrazine Containing Thiazolines and Thiazolidinones as Antitubercular and Antibacterial Agents

QSAR and Docking Studies on Propenone Derivatives as Dual COX and 5- LOX Inhibitors

BICEPS another score for the assessment of severity of liver cirrhosis

Impact of Non-sedation in Gastrointestinal Conventional Endoscopy Practices in Outpatient Setup