Peptic ulcer disease (PUD) is a multifactorial and complex disease caused by an imbalance of protective and aggressive factors (endogenous and exogenous). Despite advances in recent years, it is still responsible for substantial mortality and triggering clinical problems. Over the last decades, the understanding of PUD has changed a lot with the discovery of Helicobacter pylori infection. However, this disease continues to be a challenge due to side-effects, incidence of relapse from use of various anti-ulcer medicines, and the rapid appearance of antimicrobial resistance with current H. pylori therapies. Consequently, there is the need to identify more effective and safe anti-ulcer agents. The search for new therapies with natural products is a viable alternative and has been encouraged. The literature reports the importance of monoterpenes based on the extensive pharmacological action of this class, including wound healing and anti-ulcerogenic agents. In the present study, 20 monoterpenes with anti-ulcerogenic properties were evaluated by assessing recent in vitro and in vivo studies. Here, we review the anti-ulcer effects of monoterpenes against ulcerogenic factors such as ethanol, nonsteroidal anti-inflammatory drugs (NSAIDs), and Helicobacter pylori, highlighting challenges in the field.Biomolecules 2020, 10, 265 2 of 18 PUD results from an imbalance in mucosal defensive factors, such as mucus secretion, bicarbonate efflux, endogenous antioxidant, cell regeneration, continuous synthesis and release of prostaglandin E 2 (PGE 2 ), nitric oxide (NO), and sulfhydryl compounds (SH); and aggressive agents such as smoking, alcohol consumption, dietary factors, stress, prolonged and excessive intake of nonsteroidal anti-inflammatory drugs (NSAIDs), and Helicobacter pylori (H. pylori) infection, among others [6][7][8][9]. For a long time, it was believed that the main factor implicated in the development and progression of peptic ulceration was an hypersecretory acidic environment and together with dietary factors and/or stress was thought to cause most of PUD. But the discovery of H. pylori infection and the widespread use of NSAIDs in the second half of the 20 th century changed this perception. In recent years, peptic ulcer has been found to have multiple causes-H. pylori infection, NSAIDs, smoking, alcohol consumption, stress, lifestyle, and genetic predispositions are determined as major risk factors for the development of PUD [2]. PathophysiologyUnder normal conditions, gastric and duodenal mucosa integrity is maintained by the mucus-bicarbonate barrier, the neutral pH, and continuous epithelial cell renewal [10,11]. PGE 2 stimulates cell proliferation, mucus, and bicarbonate production, promoting a crucial function in mucosa preservation. Another vital factor in gastric homeostasis is adequate blood flow. The NO and PGs are responsible for the maintenance of proper perfusion to the gastric mucosa, assuring the delivery of oxygen and nutrients, as well as removing toxic metabolites, preventing damages to the ti...

Citral is a mixture of the two monoterpenoid isomers (neral and geranial) widely used as a health-promoting food additive safe for human and animal (approved by the US Food and Drug Administration). In vitro studies have reported on the capability of citral to reduce inflammation. Here, we report antipyretic effects of citral in vivo using the most well-accepted model of sickness syndrome, i.e., systemic administration of lipopolysaccharide ( LPS ) to rats. Citral given by gavage caused no change in control euthermic rats (treated with saline) but blunted most of the assessed parameters related to the sickness syndrome [fever (hallmark of infection), plasma cytokines (IL-1β, IL-6, and TNF-α) release, and prostaglandin E (PGE) synthesis (both peripherally and hypothalamic)]. Moreover, LPS caused a sharp increase in plasma corticosterone levels that was unaltered by citral. These data are consistent with the notion that citral has a corticosterone-independent potent antipyretic effect, acting on the peripheral febrigenic signaling (plasma levels of IL-1β, IL-6, TNF-α, and PGE), eventually down-modulating hypothalamic PGE production.

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Citral is a mixture of monoterpenes present in the essential oil of several plants, such as Cymbopogon citratus and Zingiber officinale, possessing anti-inflammatory, anti-ulcerogenic, and antipyretic actions. We investigated the action of citral on body temperature (Tb) and inflammatory signaling in eutrophic and obese mice during Systemic Inflammation (SI) induced by Lipopolysaccharide (LPS). Thus, we assessed the effect of citral (25, 100, and 300 mg/kg) and ibuprofen in LPS-induced SI in Swiss male mice fed a standard diet (SD) or high-fat diet (HFD) for 12 weeks. Following SI induction, we measured Tb and collected the serum, hypothalamus, and gastric mucosa for biochemical measurements. Acute treatment with citral decreased the Tb of both SD and HFD-fed animals. Citral (300 mg/kg) treatment caused a significantly lower Tb variation in HFD-fed animals than in those fed the SD. Citral reduced peripheral levels of tumor necrosis factor (TNF)-α in SD and HFD mice and decreased serum leptin concentration in HFD mice 90 min after the LPS challenge. Furthermore, citral also reduced interleukin (IL)-6 levels in the hypothalamus of obese mice. In summary, citral effectively reduced Tb during SI by reducing inflammatory mediators with a distinct action profile in HFD mice when compared with SD.

Obesity is linked to an inflammatory process in the different tissues of the body, including hypothalamic regions that are crucial for energy homeostasis. Citral, is a monoterpene with anti-inflammatory, antioxidant and other activities. The aim of the present study was to evaluate the effect of citral on hypothalamic inflammation triggered by obesity in male Swiss mice, and to determine the effect of citral on the concentration of pro-inflammatory mediators in the tissue. Obese male Swiss mice were treated orally with citral (25, 100 and 300 mg/kg) for seven, 14 and 21 consecutive days. Hypothalamus samples were used to determine cytokines IL-1β, TNF-α, IL-6. Hypothalamic inflammation was not installed in the Swiss mice. There are different studies that report the anti-inflammatory action of citral, as well as its action on the body weight of obese mice, however C57BL/6J mice have a better profile in the investigation of indicative parameters of diet-induced obesity. An analysis of the action of citral on hypothalamic inflammation and evolution of body weight in other strain, like C57BL/6J mice is relevant.

Obesity causes low-grade inflammation that results in the development of comorbidities. In people with obesity, exacerbation of gastric lesion severity and delayed healing may aggravate gastric mucosal lesions. Accordingly, we aimed to evaluate the citral effects on gastric lesion healing in eutrophic and obese animals. C57Bl/6 male mice were divided into two groups: animals fed a standard diet (SD) or high-fat diet (HFD) for 12 weeks. Gastric ulcers were induced using acetic acid (80%) in both groups. Citral (25, 100, or 300 mg/kg) was administered orally for 3 or 10 days. A vehicle-treated negative control (1% Tween 80, 10 mL/kg) and lansoprazole-treated (30 mg/kg) were also established. Lesions were macroscopically examined by quantifying regenerated tissue and ulcer areas. Matrix metalloproteinases (MMP-2 and -9) were analyzed by zymography. The ulcer base area between the two examined periods was significantly reduced in HFD 100 and 300 mg/kg citral-treated animals. In the 100 mg/kg citral-treated group, healing progression was accompanied by reduced MMP-9 activity. Accordingly, HFD could alter MMP-9 activity, delaying the initial healing phase. Although macroscopic changes were undetectable, 10-day treatment with 100 mg/kg citral exhibited improved scar tissue progression in obese animals, with reduced MMP-9 activity and modulation of MMP-2 activation.

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The new coronavirus pneumonia (COVID-19) is characterized by hemodynamic changes with a large release of inflammatory mediators, that inducing a systemic inflammation response (SI). Thus, SI can be induced by peripheral injection of lipopolysaccharide (LPS) in rodents, which promote the increase of systemic inflammatory mediators that induced an essential survival effector response, such as fever. Myrcene (MCN) is a monoterpene with anti-inflammatory, antioxidant, and analgesic actions are described. Our aim was to evaluate the MCN effect in euthermic rats against SI induced by low-dose LPS. Male Wistar rats were used to assess body temperature (Tb) by dataloggers. The animals were orally treated with Tween 80-1% (Tw; 10 mL/kg) or MCN (7.5 mg/kg) 30 min before the i.p. administration of induction with LPS (100 µg/kg) or Saline (1 mL/kg). After 360 min, the rats were sacrificed to evaluate the inflammatory mediators' levels through Multiplex assay. Rats in the Tw+LPS group present a significant increase in Tb when compared to the control group (Tw+Saline). The MCN treatment was