Background: Medicinal plants have a long history and are still the mainstay of the world population for combating different ailments of both human and livestock diseases. In Ethiopia, the majority populations relied on traditional medicine for various ailments of which the herbal remedies are the major means for the treatment of different diseases. Among the medicinal plants, some remedies are employed for the primary health care by the community for ailments such as flu, common cold to relief generalized pain, headache, fever, cough and others symptoms.

Objective: The present study is therefore aimed to evaluate toxic effect (safety) in laboratory mice besides microbial quality and safety physico-chemical quality control parameters and sensorial acceptability in addition to the symptomatic relief effects (analgesics, antipyretic and anti-inflammatory) of medicinal herbs blend formulations.

Methods: The acute and sub-acute toxicity studies were undertaken as per OECD guidelines Physical observations and animal body weight measurement were undertaken besides gross pathology examination, histopathology, clinical chemistry and hematology tests following the experimental period. The medicinal herb blend preparations were also administered as a single dose by oral gavage to evaluate the symptomatic relief effects (analgesics, antipyretic and anti-inflammatory). The microbial quality and safety, physicochemical quality control parameters and sensorial acceptability of the preparations were also evaluated using the standard protocol. Experimental data were analyzed by statistical software. Results were summarized as mean ± standard error of mean. One-way analysis of variance (ANOVA) and least significant difference tests will be employed to check the significant differences between the various parameters of the groups.

Result and conclusion: Oral administration of medicinal herb blend tea infusion showed no treatment-related morbidity and mortality in mice up to the dose of 10,000 mg/kg during the acute phase of the study.  Similarly, the acute toxicity study of the essential oil of medicinal herb blends drops in aqueous solution as oral gargles and essential oil drops in aqueous solution as steam inhalation were also did not show neither observed toxic signs and behavioral change nor mortality up to the dose of 5 drops and 2.5 drops of the medicinal herb blends essential oil prepared in 20ml aqueous solution, respectively. In the sub-acute toxicity studies of the herbal tea infusion no treatment-related toxic signs, and behavioral change and mortality were observed during the experimental period. The gross pathology, vital organs weight and hematology, clinical chemistry and histopathology did not show significant variation between the controls and treatment groups. The medicinal herb blends possessed analgesic, antipyretic, anti-inflammatory even and antimicrobial properties. The results also showed that the microbial quality and safety was within prescribed limits of International pharmacopeia and WHO requirements. The tea infusion and the oral gargle showed good preference ranking for sensory evaluation indicating accepted palatability.

Key words: Medicinal plants, herbal blend formulation, toxicity studies, physicochemical quality, microbial quality and safety, symptomatic relief