Rice husk, a rice processing byproduct generated in large quantities (∼20% of the grain weight), creates a major disposal problem for the rice industry. However, rice husk contains high-value bioactive compounds that can provide potential health benefits. The objective of this study was to extract high-value phenolic compounds from rice husk using supercritical carbon dioxide (SC-CO 2 ) technology. In this study, the effects of different extraction conditions, namely, temperature (40 and 60 °C), pressure (30 and 40 MPa), and ethanol concentration (15 and 25%, w/w) on the total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity (AA) were investigated. The extraction of phenolic compounds was also studied using different SC-CO 2 modifiers, i.e., ethanol and ethanol-water. The highest TPC, TFC, and AA were achieved with 30 MPa, 60 °C, and 25% ethanol-water (50%, v/v) cosolvent mixture as 1.29 mg gallic acid equivalent (GAE)/g, 0.40 mg catechin equivalent (CE)/g, and 0.23 mg Trolox equivalent (TE)/g, respectively. Increasing water content up to 50% (v/v) in the cosolvent significantly improved the extraction yield. p -Coumaric, ferulic, and syringic acids were the predominant phenolic acids in the extracts obtained by cosolvent-modified SC-CO 2 and methanol extractions. In addition, ethanol-water-modified SC-CO 2 increased rice husk's porosity, which could be a potential pretreatment to enhance cellulose extraction. Thus, ethanol-water-modified SC-CO 2 can be utilized to recover polar bioactive compounds from food processing byproducts for developing functional foods while eliminating the use of toxic organic solvents.

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Depression is one of the most frequently observed psychological disorders, affecting thoughts, feelings, behavior and a sense of well-being in person. As per the WHO, it is projected to be the primitive cause of various other diseases by 2030. Clinically, depression is treated by various types of synthetic medicines that have several limitations such as side-effects, slow-onset action, poor remission and response rates due to complicated pathophysiology involved with depression. Further, clinically, patients cannot be given the treatment unless it affects adversely the job or family. In addition, synthetic drugs are usually single targeted drugs. Unlike synthetic medicaments, there are many plants that have flavonoids and producing action on multiple molecular targets and exhibit anti-depressant action by affecting multiple neuronal transmissions or pathways such as noradrenergic, serotonergic, GABAnergic and dopaminergic; inhibition of monoamine oxidase and tropomyosin receptor kinase B; simultaneous increase in nerve growth and brain-derived neurotrophic factors. Such herbal drugs with flavonoids are likely to be useful in patients with sub-clinical depression. This review is an attempt to analyze pre-clinical studies, structural activity relationship and characteristics of reported isolated flavonoids, which may be considered for clinical trials for the development of therapeutically useful antidepressant.

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Depression is a serious disorder that affects hundreds of millions of people around the world and causes poor quality of life, problem behaviors, and limitations in activities of daily living. Therefore, the search for new therapeutic options is of high interest and growth. Research on the relationship between depression and oxidative stress has shown important biochemical aspects in the development of this disease. Flavonoids are a class of natural products that exhibit several pharmacological properties, including antidepressant-like activity, and affects various physiological and biochemical functions in the body. Studies show the clinical potential of antioxidant flavonoids in treating depressive disorders and strongly suggest that these natural products are interesting prototype compounds in the study of new antidepressant drugs. So, this review will summarize the chemical and pharmacological perspectives related to the discovery of flavonoids with antidepressant activity. The mechanisms of action of these compounds are also discussed, including their actions on oxidative stress relating to depression.

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This review article focuses on pre-clinical and clinical studies with some selected Brazilian medicinal plants in different areas of interest, conducted by research groups in Brazil and abroad. It also highlights the Brazilian market of herbal products and the efforts of Brazilian scientists to develop new phytomedicines. This review is divided into three sections. The section I describes the Brazilian large biodiversity and some attempts of Brazilian scientists to assess the pharmacological profile of most plant extracts or isolated active principles. Of note, Brazilian scientists have made a great effort to study the Brazilian biodiversity, especially among the higher plants. In fact, more than 10,000 papers were published on plants in international scientific journals between 2011 and 2013. This first part also discussed the main efforts to develop new medicines from plants, highlighting the Brazilian phytomedicines market. Despite the large Brazilian biodiversity, notably with the higher plants, which comprise over 45,000 species (20-22% of the total worldwide), and the substantial number of scientific publications on medicinal plants, only one phytomedicine is found in the top 20 market products. Indeed, this market is still only worth about 261 million American dollars. This represents less than 5% of the global Brazilian medicine market. The section II of this review focus on the use of Brazilian plant extract and/or active principles for some selected diseases, namely: central nervous systems disorders, pain, immune response and inflammation, respiratory diseases, gastrointestinal tract and metabolic diseases. Finally, section III discusses in more details some selected Brazilian medicinal plants including: Cordia verbenacea, Euphorbia tirucalli, Mandevilla velutina, Phyllanthus spp., Euterpe oleracea, Vitis labrusca, Hypericum caprifoliatum and Hypericum polyanthemum, Maytenus ilicifolia, Protium kleinii and Protium heptaphylium and Trichilia catigua. Most of these publications are preliminary and only report the effects of crude extracts, both in vitro and in vivo studies. Only very few studies have been dedicated to investigate the mechanisms of action of isolated compounds. Likewise, studies on safety (toxicology), pharmacokinetic, and especially on well-conducted clinical trials are rare. In conclusion, in spite of the abundant Brazilian biodiversity and the thousands of academic publications on plants in international peer-reviewed scientific journals, few patents and medicines have been derived from such studies. Undoubtedly, great efforts must be made to improve the development of plant-derived medicine market in Brazil, especially by involving the partnership between academia and pharmaceutical companies.

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A crude (ECH) and a purified cyclohexane extract (HCP) of Hypericum caprifoliatum and their main phloroglucinol derivative (HC1) were evaluated regarding their action on monoaminergic systems, more precisely on dopamine. In rats and mice forced swimming test, ECH and HCP dose-dependently reduced the immobility time. The effect of the highest dose was prevented by a prior administration of either sulpiride or SCH 23390 (D(2) and D(1) dopamine receptor antagonist, respectively). HCP (360 mg/kg) decreased the locomotor activity of mice. ECH (90 mg/kg) caused hypothermia and potentiated apomorphine-induced (16 mg/kg) hypothermia in mice. HCP and HC1 inhibited, in a concentration-dependent and monophasic manner, the [(3)H]-DA, [(3)H]-NA and [(3)H]-5HT synaptosomal uptakes, but did not prevent the binding of specific ligands to the monoamine transporters. Moreover, when tested at the concentrations corresponding to its IC(50) on [(3)H]-DA uptake, HC1 did not induce a significant [(3)H]-DA release, while at a higher concentration (200 ng/ml) it enhanced significantly (by 12%) the synaptosomal DA release. These data suggest that the antidepressant-like effect of H. caprifoliatum on the forced swimming test is due to an increase in monoaminergic transmission, resulting from monoamine uptake inhibition, more potently of dopamine, which may be related to their phloroglucinol contents.

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