Immunomodulatory effect of protocatechuic acid on cyclophosphamide induced brain injury in rat: Modulation of inflammosomes NLRP3 and SIRT1

Metformin improves cognitive dysfunction through SIRT1/NLRP3 pathway-mediated neuroinflammation in db/db mice

Diabetes mellitus (DM), an important public health problem, aggravates the global economic burden. Diabetic encephalopathy (DE) is a serious complication of DM in the central nervous system. Metformin has been proven to improve DE. However, the mechanism is still unclear. In this study, the db/db mice, a common model used for DE, were employed to explore and study the neuroprotective effect of metformin and related mechanisms. Behavioral tests indicated that metformin (100 or 200 mg/kg/day) could significantly improve the learning and memory abilities of db/db mice. The outcomes from the oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) demonstrate that metformin effectively modulates glucose and insulin signaling pathways in db/db mice. The results of body weight and blood lipid panel (total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol) show that metformin promotes the level of lipid metabolism in db/db mice. Furthermore, data from oxidative stress assays, which measured levels of malondialdehyde, superoxide dismutase, catalase, and glutathione peroxidase, suggest that metformin suppresses oxidative stress-induced brain damage in db/db mice. In addition, western blot, Nissl staining, and immunofluorescence results showed that metformin increased the expressions of nerve growth factor and postsynaptic density 95 and repaired neuronal structural damage. For the mechanism study, metformin activated SIRT1 and inhibited the expression of NLRP3 inflammasome (NLRP3, ASC, caspase-1, IL-1β, and IL-18) and inflammatory cytokines (TNFα and IL-6). In conclusion, metformin could ameliorate cognitive dysfunction through the SIRT1/NLRP3 pathway, which might be a promising mechanism for DE treatment.

Magnetic targeting of lornoxicam/SPION bilosomes loaded in a thermosensitive in situ hydrogel system for the management of osteoarthritis: Optimization, in vitro, ex vivo, and in vivo studies in rat model via modulation of RANKL/OPG

Osteoarthritis is a bone and joint condition characterized pathologically by articular cartilage degenerative damage and can develop into a devastating and permanently disabling disorder. This investigation aimed to formulate the anti-inflammatory drug lornoxicam (LOR) into bile salt-enriched vesicles loaded in an in situ forming hydrogel as a potential local treatment of osteoarthritis. This was achieved by formulating LOR-loaded bilosomes that are also loaded with superparamagnetic iron oxide nanoparticles (SPIONs) for intra-muscular (IM) administration to improve joint targeting and localization by applying an external magnet to the joint. A 31.22 full factorial design was employed to develop the bilosomal dispersions and the optimized formula including SPION (LSB) was loaded into a thermosensitive hydrogel. Moreover, in vivo evaluation revealed that the IM administration of LSB combined with the application of an external magnet to the joint reversed carrageen-induced suppression in motor activity and osteoprotegerin by significantly reducing the elevations in mitogen-activated protein kinases, extracellular signal-regulated kinase, and receptor activator of nuclear factor kappa beta/osteoprotegerin expressions. In addition, the histopathological evaluation of knee joint tissues showed a remarkable improvement in the injured joint tissues. The results proved that the developed LSB could be a promising IM drug delivery system for osteoarthritis management.

Tannic acid coated nanosuspension for oral delivery of chrysin intended for anti-schizophrenic effect in mice

Chrysin is a flavonoid drug with numerous therapeutic activities. It suffers from low intestinal absorption owing to its hydrophobicity. Therefore, the aim of this study is to exploit the efficient technique of nanosuspension (NSP) to formulate chrysin-NSP coated with tannic acid (TA) to improve the solubility and anti-schizophrenic activity of chrysin. A 23 full factorial design was constructed where the independent factors were type of polymer, surfactant concentration (0.5 or 1 %) and the aqueous phase volume (5 or 15 mL), while the dependent responses were the particle size (PS) of the obtained formulation as well as the % chrysin dissolved after 2 h (Q2h). The optimum formulation (NSP-4) composed of 1 % PEG 400 and 1 % Cremophor RH40 in 15 mL aqueous phase. It achieved a PS and Q2h values of 108.00 nm and 38.77 %, respectively. NSP-4 was then coated with TA (TA-coated NSP-4) for further enhancement of chrysin solubility. TA-coated NSP-4 revealed PS and zeta potential values of 150 ± 14 nm and -32.54 ± 2.45 mV, respectively. After 6 h, chrysin dissolved % were 53.97 and 80.22 for uncoated NSP-4 and TA-coated NSP-4, respectively, compared with only 9.47 for free chrysin. The developed formulations and free chrysin were assessed regarding their effect on schizophrenia induced in mice by cuprizone (CPZ). Treatment with the developed formulations and free chrysin ameliorated demyelination and behavioral deficit induced by CPZ via elevating MBP and PI3K/PKC activities as well as reducing GFAP expression levels. The developed formulations and free chrysin inhibited Galactin-3 and TGF-β expressions and stimulated GST antioxidant enzyme. Furthermore, they maintained the balances in glutamatergic and dopaminergic neurotransmission via modulation on neuregulin-1 and alleviated nuclear pyknosis and degeneration in the neurons. The order of activity was: TA-coated NSP-4 > NSP-4 > free chrysin.

Role of SIRT1 in Potentially Toxic Trace Elements (Lead, Fluoride, Aluminum and Cadmium) Associated Neurodevelopmental Toxicity

The formation of the central nervous system is a meticulously planned and intricate process. Any modification to this process has the potential to disrupt the structure and operation of the brain, which could result in deficiencies in neurological growth. When neurotoxic substances are present during the early stages of development, they can be exceptionally dangerous. Prenatally, the immature brain is extremely vulnerable and is therefore at high risk in pregnant women associated with occupational exposures. Lead, fluoride, aluminum, and cadmium are examples of possibly toxic trace elements that have been identified as an environmental concern in the aetiology of a number of neurological and neurodegenerative illnesses. SIRT1, a member of the sirtuin family has received most attention for its potential neuroprotective properties. SIRT1 is an intriguing therapeutic target since it demonstrates important functions to increase neurogenesis and cellular lifespan by modulating multiple pathways. It promotes axonal extension, neurite growth, and dendritic branching during the development of neurons. Additionally, it contributes to neurogenesis, synaptic plasticity, memory development, and neuroprotection. This review summarizes the possible role of SIRT1 signalling pathway in potentially toxic trace elements -induced neurodevelopmental toxicity, highlighting some molecular pathways such as mitochondrial biogenesis, CREB/BDNF and PGC-1α/NRF1/TFAM.

Phytochemical Elucidation and Effect of Maesa indica (Roxb.) Sweet on Alleviation of Potassium Dichromate-Induced Pulmonary Damage in Rats

Maesa indica (Roxb.) Sweet is one of the well-known traditionally-used Indian plants. This plant is rich in secondary metabolites like phenolic acids, flavonoids, alkaloids, glycosides, saponins, and carbohydrates. It contains numerous therapeutically active compounds like palmitic acid, chrysophanol, glyceryl palmitate, stigmasterol, β-sitosterol, dodecane, maesaquinone, quercetin 3-rhaminoside, rutin, chlorogenic acid, catechin, quercetin, nitrendipine, 2,3-dihydroxypropyl octadeca-9,12-dienoate, kiritiquinon, and β-thujone. The Maesa indica plant has been reported to have many biological properties including antidiabetic, anticancer, anti-angiogenic, anti-leishmanial, antioxidant, radical scavenging, antibacterial, antiviral, and anti-coronavirus effects. One purpose of the current study was to investigate the leaves' metabolome via Triple-Time-of-Flight-Liquid-Chromatography-Mass Spectrometry (T-TOF LC/MS/MS) to identify the chemical constituents of the Maesa indica ethanolic extract (ME). Another purpose of this study was to explore the protective effect of ME against potassium dichromate (PD)-induced pulmonary damage in rats. Rats were assigned randomly into four experimental groups. Two different doses of the plant extract, (25 and 50 mg/kg), were administered orally for seven consecutive days before PD instillation injection. Results of our study revealed that ME enhanced cellular redox status as it decreased lipid peroxidation marker, MDA and elevated reduced glutathione (GSH). In addition, ME upregulated the cytoprotective signaling pathway PI3K/AKT. Moreover, ME administration ameliorated histopathological anomalies induced by PD. Several identified metabolites, such as chlorogenic acid, quercetin, apigenin, kaempferol, luteolin, and rutin, had previously indicated lung-protective effects, possibly through an antioxidant effect and inhibition of oxidative stress and inflammatory mediators. In conclusion, our results indicated that ME possesses lung-protective effects, which may be the result of its antioxidant and anti-inflammatory properties.

Phytochemical profiling and neuroprotective activity of Callistemon subulatus leaves against cyclophosphamide-induced chemobrain

Cyclophosphamide (CPA) is a chemotherapeutic drug used for various types of cancers. However, patients receiving CPA for long periods suffer cognitive impairment associated with difficulties in learning, decreased concentration, and impaired memory. Chemotherapy-induced cognitive impairment, known as chemobrain, has been attributed to enhanced oxidative stress and inflammatory response. The current study aimed to identify the phytoconstituents of Callistemon subulatus extract (CSE) using HPLC-ESI/MS-MS analysis and evaluate its neuroprotective activity against CPA-induced chemobrain in rats. Fourteen compounds were identified following HPLC analysis including, five phlorglucinols, four flavonol glycosides, a triterpene, and a phenolic acid. Forty rats were divided into five groups treated for ten days as follows; group I (control group), group II received CPA (200 mg/kg, i.p.) on the 7th day, groups III and IV received CSE (200 and 400 mg/kg respectively, orally) for ten days and CPA (200 mg/kg, i.p.) on the 7th day, and group V received only CSE (400 mg/kg, orally) for ten days. The administration of CSE effectively ameliorated the deleterious effects of CPA on spatial and short-term memories, as evidenced by behavioral tests, Y-maze and passive avoidance. Such findings were further confirmed by histological examination. In addition, CSE counteracted the effect of CPA on hippocampal acetylcholinesterase (AChE) activity enhancing the level of acetylcholine. Owing to the CSE antioxidant properties, it hindered the CPA-induced redox imbalance, which is represented by decreased catalase and reduced glutathione levels, as well as enhanced lipid peroxidation. Therefore, CSE may be a promising natural candidate for protection against CPA-induced chemobrain in cancer patients.

Coating with tripolyphosphate-crosslinked chitosan as a novel approach for enhanced stability of emulsomes following oral administration: Rutin as a model drug with improved anti-hyperlipidemic effect in rats

The aim of the current study is to preserve the emulsomal vesicles against the harsh condition of gastrointestinal tract (GIT), after oral administration, employing tripolyphosphate (TPP)-crosslinked chitosan as a protective coating layer. Rutin was used as a model drug with evaluation of anti-hyperlipidemic activity in rats. The rutin loaded unmodified emulsomes were prepared using tripalmitin and soybean phosphatidylcholine (SPC), by thin film method. Drug loading for the prepared formulations ranged between 6.80 and 15.50 %. The selected formulation (RT-Emuls-6) comprised tripalmitin and SPC, molar ratio 1:1, and exhibited particle size (PS) and zeta potential (ZP) of 150.40 nm and -35.35 mV, respectively. RT-Emuls-6 was then modified by coating with either solely chitosan (RT-Emuls-6-Ch) or TPP-crosslinked chitosan (RT-Emuls-6-Ch-TPP-1). The latter exhibited PS and ZP values of 269.60 nm and 37.17 mV, respectively. Transmission electron microscopy of RT-Emuls-6-Ch-TPP-1 showed a dense pale greyish layer of a coating layer of chitosan crosslinked with TPP surrounding SPC bilayers. Fourier transform infrared spectroscopy analysis along with X-ray powder diffraction confirmed cross-linking between chitosan and TPP. Stability study in the simulated GIT fluids revealed that the order of rutin retained percentage was RT-Emuls-6-Ch-TPP-1 > RT-Emuls-6-Ch > RT-Emuls-6 (80.02, 50.66 and 44.41 %, respectively for simulated gastric fluid and 63.50, 55.66 and 24.00 %, respectively for simulated intestinal fluid, after 2 h incubation). Anti-hyperlipidemic activity of rutin loaded emulsomes was evaluated, after oral administration, in a high fat diet-induced hyperlipidemia in rats. The order of activity was as follows: RT-Emuls-6-Ch-TPP-1 > RT-Emuls-6-Ch > RT-Emuls-6 > free rutin. These findings revealed the potential of TPP-crosslinked chitosan as a protective coating layer for enhancing the stability of emulsomes against the harsh condition of GIT. RT-Emuls-6-Ch-TPP-1 had a potent anti-hyperlipidemic activity via regulation of lipids, oxidative stress, irisin and uncoupling protein 1.

Neuroprotective effect of quercetin and nano-quercetin against cyclophosphamide-induced oxidative stress in the rat brain: Role of Nrf2/ HO-1/Keap-1 signaling pathway

Quercetin (Qu) is a powerful flavanol antioxidant that is naturally found in plants and is part of the flavonoid family. Qu has a wide range of biological properties, such as neuroprotective, anti-cancer, anti-diabetic, anti-inflammatory, and radical scavenging capabilities. However, the in vivo application of Qu is limited by its poor water solubility and low bioavailability. These issues could be addressed by utilizing Qu nanoformulations. Cyclophosphamide (CP) is a potent chemotherapeutic agent that causes severe neuronal damage and cognitive impairment due to reactive oxygen species (ROS) overproduction. The present study aimed to explore the proposed neuroprotective mechanism of quercetin (Qu) and quercetin-loaded Chitosan nanoparticles (Qu-Ch NPs) against the brain oxidative damage induced by CP in male albino rats. For this aim, thirty-six adult male rats were randomly divided into six groups (n = 6). Rats were pretreated with Qu and Qu-Ch NPs orally in doses of 10 mg/kg bwt/day for 2 weeks, and CP (75 mg/kg bwt) was administered intraperitoneally 24 h before the termination of the experiment. After 2 weeks, some neurobehavioral parameters were evaluated, and then euthanization was done to collect the brain and blood samples. Results showed that CP induces neurobehavioral deteriorations and impaired brain neurochemical status demonstrated by a significant decrease in brain glutathione (GSH), serum total antioxidant capacity (TAC), and serotonin (5-HT) levels while malondialdehyde (MDA), nitric oxide (NO), Tumor necrosis factor α (TNFα), and choline esterase (ChE) concentrations increased significantly compared to the control group. Pretreatment with Qu and Qu-Ch NPs showed a significant anti-oxidative, anti-depressive, and neuroprotective effect through modification of the above-mentioned parameters. The results were further validated by assessing the expression levels of selected genes in brain homogenates and histopathological investigations were done to pinpoint the exact brain-altered regions. It could be concluded that Qu and Qu-Ch NPs can be useful neuroprotective adjunct therapy to overcome neurochemical damage induced by CP.

Topical caffeine-loaded nanostructured lipid carriers for enhanced treatment of cellulite: A 32 full factorial design optimization and in vivo evaluation in rats

The goal of this study was the development and evaluation of semisolid caffeine (CAF) loaded nanostructured lipid carriers (NLCs) for topical treatment of cellulite. CAF-loaded NLC formulations were prepared via high-speed homogenization followed by ultrasonication. A 32 full factorial design was employed for formulation optimization. The total lipid content (%) and the liquid lipid content per total lipids (%) were chosen as factors, whereas particle size (PS), polydispersity index (PDI), zeta potential (|ZP|) and viscosity (VIS) were selected as responses. The design suggested CAF-NLC3 as the optimum formulation consisting of a total lipid content of 15% w/w (palmitic acid and soft paraffin/isopropyl myristate, 7:3 w/w) and a surfactant content of 10% w/w (Tween 80/lecithin, 8:1.2 w/w). CAF-NLC3 revealed PS, PDI, ZP, VIS and CAF content values of 318.8 nm, 0.253, -41.1 mV, 18.0 Pa.s and 97.57%, respectively. It showed a pseudoplastic rheological behavior, acceptable pH value (5.25), good spreadability (1.12 mm2/g) and spherical shape employing transmission electron microscopy. Differential scanning calorimetry and X-ray diffraction demonstrated the amorphization of CAF in CAF-NLC3. CAF-NLC3 remained stable for 3 months at room and refrigeration conditions. A single topical application of CAF-NLC3 on shaved abdominal skins of Wistar rats revealed enhanced skin retention of CAF by 2-fold and 1.4-fold after 4 h when compared with plain CAF gel (CAF-P) and marketed CAF gel (CAF-M), respectively. Furthermore, CAF-NLC3 exhibited a superior anti-cellulite activity in comparison with CAF-P and CAF-M through elevating extracellular matrix components (collagen 1, elastin and hyaluronic acid) and stimulating the brown adipose tissue thermogenesis via up-regulating UCP1 and PPAR-γ expression. In addition, CAF-NLC3 prominently increased lipolysis through HSL activity and decreased pro-inflammatory cytokines such as ICAM-1 and VCAM-1 after 30 days of treatment on a high fat diet-induced cellulite rat model. These findings were further confirmed by histopathological examination supported by morphometric analysis. Therefore, incorporation of CAF in a semisolid NLC formulation would be a promising cosmetic approach for the topical treatment of cellulite.

Molecular mechanisms underlying cyclophosphamide-induced cognitive impairment and strategies for neuroprotection in preclinical models

Cyclophosphamide has drastically enhanced the expectancy and quality of life of cancer patients. However, it is accompanied by diverse neurological complications which are considered a dose-limiting adverse effect. Neurotoxicity caused by cyclophosphamide can manifest in numerous manners including anxiety, depression, motor dysfunction and cognitive deficits. This review article offers an overview on cyclophosphamide-induced neurotoxicity, providing a unified point of view on the possible underlying molecular mechanisms including oxidative brain damage, neuroinflammation, apoptotic neuronal cell death as well as disruption of the balance of brain neurotransmitters and neurotrophic factors. Besides, this review sheds light on the promising protective agents that have been investigated using preclinical animal models as well as their biological targets and protection mechanisms. Despite promising results in experimental models, none of these agents has been studied in clinical trials. Thus, there is lack of evidence to advocate the use of any neuroprotective agent in the clinical setting. Furthermore, none of the protective agents has been evaluated for its effect on the anticancer activity of cyclophosphamide in tumor-bearing animals. Therefore, there is a great necessity for adequate well-designed clinical studies for evaluation of the therapeutic values of these candidates. Conclusively, this review summarizes the molecular mechanisms accounting for cyclophosphamide-induced neurotoxicity together with the potential protective strategies seeking for downgrading this neurological complication, thus enhancing the quality of life and well-being of cancer patients treated with cyclophosphamide.

Modeling and in-vivo evaluation of fibrinolytic enzyme produced by Bacillus subtilis Egy under solid state fermentation

Blood clot formation increases cases of myocardial infarction (AMI) and stroke, thus urges directing much research works for treatment and prevention of the causes. One of these directions is the microbial production of fibrinolytic enzymes as thrombolytic agents. In the current work, Bacillus subtilis Egy has been used for enzyme production under solid state fermentation. Among twelve nutrient meals in addition to wheat bran as a control fodder yeast yielded the highest enzyme activity reaching 114U/g. Applying statistical model for optimization of enzyme production revealed that 3.6%, fodder yeast; 40%, moisture content; 6 days, incubation period and 2%, inoculum size were the optimum conditions for maximum fibrinolytic enzyme production (141.02 U/g) by Bacillus subtilis Egy under solid-state fermentation The model was significant and data were experimentally validated. The produced fibrinolytic enzyme was evaluated for in vitro and in vivo cytotoxicity. In-vivo examination of the enzyme resulted in no mortality during the first 24 h after treatment. After 14 days, the results revealed no significant changes detected in hematological parameters (RBCs, MCV, hemoglobin except WBCs which showed an increase for both sexes. Histopathological examination of liver and kidney of rats received oral and subcutaneous treatments showed normal architecture. The data showed the applicability of the produced enzyme for the treatment of blood clot with no significant effect on living cells or on physiological functions.

Exploring the quality markers and mechanism of Bushen Huoxue Prescription in prevention and treatment of diabetic retinopathy based on Chinmedomics strategy

ETHNOPHARMACOLOGICAL RELEVANCE

Chinese herbal medicines have complex chemical composition; therefore, revealing the effective substances of Chinese herbal medicine becomes a prerequisite for scientific elucidation of the mechanism of action of Bushen Huoxue Prescription (BHP) against diabetic retinopathy (DR) and the development of new drugs.

AIM OF THE STUDY

The Chinmedomics technique was used to evaluate the pharmacodynamic ingredients and mechanism of action of BHP against DR rats.

MATERIALS AND METHODS

The overall physiological condition of the rats, including body weight, blood glucose, inflammatory factor levels, histological staining, and urine metabolic profile were examined to evaluate the model and its effects. The chemical composition of BHP in vivo and ex vivo was fully analyzed utilizing UPLC-Q-Exactive Orbitrap MS in conjunction with TCM serum pharmacochemistry. Finally, correlation analysis between biomarkers, and serum migration components was used to identify Quality markers (Q-markers) that were significantly associated with effectiveness.

RESULTS

The UPLC-Q-Exactive Orbitrap MS platform was used to identify a total of 29 chemicals in serum, 17 of which were highly linked with effectiveness and can be potentially employed as pharmacodynamic substances for BHP against DR. In addition, 14 biomarkers related to galactose metabolism, starch and sucrose metabolism, pantothenate and CoA biosynthesis, glycine, serine, and threonine metabolism were identified. These pathways reveal that DR may be inextricably linked to levels of oxidative stress and inflammation in the organism. Finally, five active ingredients were identified as potential Q-markers of BHP against DR, namely ajugol, protocatechuic acid, tanshinone IIA, panaxatriol and puerarin.

CONCLUSION

This study successfully clarified the efficacy and Q-markers of BHP through the Chinmedomics strategy, which is of great significance in determining the quality standards of BHP.

Eplerenone modulates the inflammatory response in monosodium iodoacetate-induced knee osteoarthritis in rats: Involvement of RANKL/OPG axis

AIMS

Osteoarthritis (OA) is a multifactorial degenerative disease marked by the progressive deterioration of articular cartilage with inflammation of the synovium. OA's main symptoms include pain and function loss. Monosodium Iodoacetate (MIA) experimental model is widely-used for OS induction since it produces symptoms comparable to those occurring in humans.

MATERIALS AND METHODS

Thirty-two rats were divided into four groups (n = 8). The 1st group received saline and included the normal-control rats. Groups 2-4 received intra-articular injections of MIA (3 mg/50 μL) in the rats' knee joints to induce OA. Group 2 included the MIA-control rats. Groups 3 and 4 received intra-articular MIA followed by a 14-day oral eplerenone (50 and 100 mg/kg); respectively.

KEY FINDINGS

Intra-articular injection of MIA in rats' knee joints caused significant inflammation and pain, elevation of Akt and ERK gene expression in knee joints along with significant alterations in the histological pictures of knee joints and OARSI scores. RANKL/OPG Axis was significantly disrupted.

SIGNIFICANCE

Eplerenone treatment produced a significant improvement in motor coordination and spontaneous locomotor activity in rats and modulated the key inflammatory mediators in OA (TNF-α, NF-κβ, and IL-6). Eplerenone also suppressed the qRT-PCR gene expression of Akt and ERK in knee joint tissues and improved the histological pictures and OARSI scores of knee joints of treated rats. Eplerenone caused a decline in RANKL concentration accompanied by a rise in OPG concentration thus modulating the RANKL/OPG Axis. Consequently, eplerenone is a candidate for OA therapy due to its potential anti-inflammatory effects.

Therapeutic Potential of Phenolic Compounds in Medicinal Plants-Natural Health Products for Human Health

Phenolic compounds and flavonoids are potential substitutes for bioactive agents in pharmaceutical and medicinal sections to promote human health and prevent and cure different diseases. The most common flavonoids found in nature are anthocyanins, flavones, flavanones, flavonols, flavanonols, isoflavones, and other sub-classes. The impacts of plant flavonoids and other phenolics on human health promoting and diseases curing and preventing are antioxidant effects, antibacterial impacts, cardioprotective effects, anticancer impacts, immune system promoting, anti-inflammatory effects, and skin protective effects from UV radiation. This work aims to provide an overview of phenolic compounds and flavonoids as potential and important sources of pharmaceutical and medical application according to recently published studies, as well as some interesting directions for future research. The keyword searches for flavonoids, phenolics, isoflavones, tannins, coumarins, lignans, quinones, xanthones, curcuminoids, stilbenes, cucurmin, phenylethanoids, and secoiridoids medicinal plant were performed by using Web of Science, Scopus, Google scholar, and PubMed. Phenolic acids contain a carboxylic acid group in addition to the basic phenolic structure and are mainly divided into hydroxybenzoic and hydroxycinnamic acids. Hydroxybenzoic acids are based on a C6-C1 skeleton and are often found bound to small organic acids, glycosyl moieties, or cell structural components. Common hydroxybenzoic acids include gallic, syringic, protocatechuic, p-hydroxybenzoic, vanillic, gentistic, and salicylic acids. Hydroxycinnamic acids are based on a C6-C3 skeleton and are also often bound to other molecules such as quinic acid and glucose. The main hydroxycinnamic acids are caffeic, p-coumaric, ferulic, and sinapic acids.