Tablet and capsule formulations incorporating high doses of a dry optimized herbal extract: The case of Satureja kitaibelii

Abstract Aerial parts of Satureja kitaibelii are traditionally used as carminative, for treatment of respiratory and urinary complaints, or as anti-inflammatory agent for skin and mucous membranes. The aim of the present study was to formulate immediate-release capsules and tablets of S. kitaibelii optimized dry extract by direct compression with a high content of optimized extract (≥95%). The influence of ethanol concentration (40–96%, v/v), temperature (25–80 °C) and time (2–8 h) on the extraction yield, total phenolic content (TPC), as well as on the contents of rosmarinic acid (RA) and clinopodic acid O (CAO) in the S. kitaibelii dry extract was investigated using the response surface methodology (RSM). The estimated optimal conditions for the extraction were: ethanol 46.4%, 61.6 °C, 2 h. Dry extract of S. kitaibelii obtained under the optimal conditions (characterized by: yield 24.2%, TPC 170.4 mg gallic acid equivalents/g, RA 10.7 mg/g and CAO 17.1 mg/g) was used to manufacture solid dosage forms. Three formulations (F) were prepared: F1, hard capsules (99% dry extract, 1% magnesium stearate); F2, uncoated tablets (99% dry extract, 1% magnesium stearate) and F3, uncoated tablets (95% dry extract, 4% sodium starch glycolate, 1% magnesium stearate). Hard capsules (F1) with the uniform weight, adequate disintegration time and dissolution rate were obtained. Regarding tablet formulations, F3 exhibited satisfactory tableting properties, disintegration time and dissolution profile. Therefore, immediate-release capsules and tablets with a high content of S.kitaibelii extract were formulated to accomplish the unmet need for convenient solid dosage forms that contains high doses of herbal extracts.