Abstract
Due to the remarkable anti-tumor activities of oridonin (Ori), research on Rabdosia rubescens has attracted more and more attention in the pharmaceutical field. The purpose of this study was to extract Ori from R. rubescens by ultrasound-assisted extraction (UAE) and prepare Ori liposomes as a novel delivery system to improve the bioavailability and biocompatibility. Response surface methodology (RSM), namely Box-Behnken design (BBD), was applied to optimize extraction conditions, formulation, and preparation process. The results demonstrated that the optimal extraction conditions were an ethanol concentration of 75.9%, an extraction time of 35.7 min, and a solid/liquid ratio of 1:32.6. Under these optimal conditions, the extraction yield of Ori was 4.23 mg/g, which was well matched with the predicted value (4.28 mg/g). The optimal preparation conditions of Ori liposomes by RSM, with an ultrasonic time of 41.1 min, a soybean phospholipids/drug ratio of 9.6 g/g, and a water bath temperature of 53.4 °C, had higher encapsulation efficiency (84.1%). The characterization studies indicated that Ori liposomes had well-dispersible spherical shapes and uniform sizes with a particle size of 137.7 nm, a polydispersity index (PDI) of 0.216, and zeta potential of −24.0 mV. In addition, Ori liposomes presented better activity than free Ori. Therefore, the results indicated that Ori liposomes could enhance the bioactivity of Ori, being proposed as a promising vehicle for drug delivery.
Highlights
Received: 16 December 2021Rabdosia rubescens Hara, which is known as Donglingcao, named Poxuedan, is mainly distributed in the dry slopes and along the streams in the northern provinces ofChina
The aim of this study is to optimize the preparation conditions of Ori liposomes and assess anti-breast cancer cell activity in vitro, which provides the theoretical basis for the further exploration, development, and utilization of Ori from R. rubescens
The Ori yield increased gradually until an ethanol concentration of 60%, when the yield reached a peak and declined. This phenomenon mainly can be attributed to a better solubility of Ori at higher ethanol concentrations
Summary
Received: 16 December 2021Rabdosia rubescens Hara, which is known as Donglingcao, named Poxuedan, is mainly distributed in the dry slopes and along the streams in the northern provinces ofChina. People use R. rubescens for gum disease, prostate, cancer, and other conditions. Oridonin (Ori), an ent-kaurane diterpenoid with formula C20 H28 O6 , is the main active ingredient isolated from the leaves of R. rubescens [1,2]. According to the literature review, Ori has antiviral, anti-tumor [2,3,4,5,6], anti-inflammation [7], and anti-bacterial properties as well as scavenging activity against oxygen free radicals [8]. It has been confirmed that Ori effectively inhibits the proliferation of more than 20 human cancer cell lines [9,10], including those from the breast [11,12], prostate [13], lung, and liver [14]. The development of new drug carriers to overcome these problems has become a hot spot in scientific research
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