Extracts from medicinal plants are widely used in the treatment and prevention of different diseases. Micromeria frivaldszkyana is a Balkan endemic species with reported antioxidant and antimicrobial characteristics; however, its phytochemical composition is not well defined. Here, we examined the metabolome of M. frivaldszkyana by chromatography–mass spectrometry (GC-MS), ultra-performance liquid chromatography–mass spectrometry (UPLC-MS-MS), and inductively coupled plasma mass spectrometry (ICP-MS). Amino acids, organic acids, sugars, and sugar alcohols were the primary metabolites with the highest levels in the plant extract. Detailed analysis of the sugar content identified high levels of sucrose, glucose, mannose, and fructose. Lipids are primary plant metabolites, and the analysis revealed triacylglycerols as the most abundant lipid group. Potassium (K), magnesium (Mg), zinc (Zn), and calcium (Ca) were the elements with the highest content. The results showed linarin, 3-caffeoil-quinic acid, and rosmarinic acid, as well as a number of polyphenols, as the most abundant secondary metabolites. Among the flavonoids and polyphenols with a high presence were eupatorin, kaempferol, and apigenin—compounds widely known for their bioactive properties. Further, the acute toxicity and potential anti-inflammatory activity of the methanolic extract were evaluated in Wistar rats. No toxic effects were registered after a single oral application of the extract in doses of between 200 and 5000 mg/kg bw. A fourteen-day pre-treatment with methanolic extract of M. frivaldszkyana in doses of 250, 400, and 500 mg/kg bw induced anti-inflammatory activity in the 1st, 2nd, and 3rd hours after carrageenan injection in a model of rat paw edema. This effect was also present in the 4th hour only in the group treated with a dose of 500 mg/kg. In conclusion, M. frivaldszkyana extract is particularly rich in linarin, rosmarinic acid, and flavonoids (eupatorin, kaempferol, and apigenin). Its methanolic extract induced no toxicity in male Wistar rats after oral application in doses of up to 5000 mg/kg bw. Additionally, treatment with the methanolic extract for 14 days revealed anti-inflammatory potential in a model of rat paw edema on the 1st, 2nd, and 3rd hours after the carrageenan injection. These results show the anti-inflammatory potential of the plant, which might be considered for further exploration and eventual application as a phytotherapeutic agent.

Recently, compounds of plant origin have been the focus of increased scientific interest. Micromeria frivaldszkyana is a rare species endemic to Bulgaria, whose biological activity remains unknown. This article aims to evaluate the subchronic toxicity of Micromeria frivaldszkyana methanolic extract and its effect on cognition in rats. Following 90 days of oral administration, a histopathological evaluation of brain, kidney, and liver tissues was conducted. Additionally, serum levels of total bilirubin (TB), conjugated bilirubin (CB), alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatinine (CR), uric acid (UA), and urea (U) were measured. Cognitive function was studied after 7 d of treatment using activity cage test, along with tests for active memory, passive memory, anxiety, spatial and working memory, and explorative activity. The experiments showed no toxic effects of the extract in subchronic application. No adverse effects on brain function were observed after 14 days of treatment. While the extract increased the motor activity of the animals, it did not significantly improve the learning and memory processes. In conclusion, the methanolic extract of Micromeria frivaldszkyana in doses 250 and 500 mg/kg bw did not induce toxicity after 90-day treatment in rats. These doses did not significantly affect central nervous system (CNS) functions, although increased motor activity was observed after 14 days of treatment with the extract.

Acetaminophen (APAP) overdose can result in potentially fatal acute liver failure, with free radical formation identified as a major mechanism of liver tissue damage. Micromeria frivaldszkyana (M. frivaldszkyana), a rare species endemic to Bulgaria, has demonstrated significant antioxidant activity. Male Wistar rats were treated orally for 7 days with saline; 250, 400, or 500 mg/kg of a water solution of dried methanolic extract of M. frivaldszkyana; 100 mg/kg rosmarinic acid (RA); or 125 mg/kg silymarin. Liver toxicity was induced by oral application of 2000 mg/kg APAP on the last day of treatment. Forty-eight hours later, blood and livers were collected for histological and biochemical analysis. The results revealed that treatment with 500 mg/kg of the dried methanolic extract significantly reduced the elevated levels of aspartate aminotransferase, alanine aminotransferase, malondialdehyde, 8-hydroxy-2′-deoxyguanosine, and tumor necrosis factor-alpha in APAP overdose. The present results clearly demonstrate, for the first time, that pre-treatment with methanolic extract of M. frivaldszkyana results in significant hepatoprotective effects in the APAP-induced rat model of liver injury. The mechanism of this effect may involve cell membrane protection, decreased lipid peroxidation and DNA damage, and attenuation of aseptic inflammation. These effects can be attributed to the main compounds identified in the extract (linarin, chlorogenic acid, rutin, eupatorin, apigenin, RA).

Plant-derived compounds have recently attracted considerable scientific attention due to their potential therapeutic applications, which are largely attributed to their antioxidant properties. Tert-butyl hydroperoxide (t-BHP) is a potent inducer of intracellular oxidative stress, generating reactive free radicals, which significantly contribute to hepatic and renal damage. Micromeria frivaldszkyana (M. frivaldszkyana), a Bulgarian endemic species, contains high levels of phenolic compounds, including linarin, rosmarinic acid (RA), chlorogenic acid, rutin, quercetin, naringenin, and apigenin. In this study, male Wistar rats received oral treatment for 5 days comprising saline, 250, 400, or 500 mg/kg of M. frivaldszkyana methanolic extract, 100 mg/kg RA, or 125 mg/kg silymarin. On the final day, 0.5 mmol/kg of t-BHP was injected intraperitoneally, and blood and liver tissue samples were collected 18 h later for biochemical and histological analysis. Liver and kidney function was evaluated using biochemical markers (alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine (Cr), uric acid (UA)), indicators of oxidative stress (malondialdehyde (MDA), 8-hydroxy-2′-deoxyguanosine (8-OHdG), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT)), and histopathology. Exposure to t-BHP resulted in significant hepatic and renal damage, including elevated serum markers, increased lipid peroxidation, and deoxyribonucleic acid (DNA) damage. Administration of 500 mg/kg M. frivaldszkyana markedly lowered elevated serum ALT and AST levels. The extract also significantly mitigated t-BHP-induced increases in serum Cr and UA. However, no significant increase in the levels of the antioxidant enzymes SOD and CAT or in GSH was observed at all tested doses. Malondialdehyde and 8-OHdG levels increased markedly following t-BHP exposure, whereas pretreatment with M. frivaldszkyana at all tested doses significantly ameliorated these oxidative alterations. These findings suggest that the methanolic extract of M. frivaldszkyana confers protective effects against t-BHP-induced toxicity, potentially through stabilisation of cell membranes, inhibition of lipid peroxidation, and reduction in DNA damage. The extract may therefore serve as a potential natural therapeutic agent against injuries caused by oxidative stress.