A Study On Preparation And Anti-inflammatory Pharmacodynamics Evaluation Of Andrographolide Microemulsion

Andrographis paniculata（Burm.f）Nees,commonly known as‘king of bitters’,is a herbaceous plant belonging to the Family Acanthaceae.It has been widely used in Asian countries including China,India,Thailand and Malaysia for the treatment of sore throat and upper respiratory tract infections.Andrographolide,an active ingredient from Andrographis paniculata,is a diterpenoid with a molecular formula of C₂₀H₃₀O₅ and a relative molecular mass of 350.45.Andrographolide has been shown broad pharmacological activities including anti-inflammation,anti-virus,anti-cancer,liver-protecting and etc,and has been extensively used in clinical practice.However,the application of clinical was discounted by its poor water solubility and low bioavailability after oral administration.Therefore,the development of novel pharmaceutical preparation for improving the bioavailability of andrographolide is highlighted.In this study,a self-microemulsifying drug delivery system（SMEDDS）containing andrographolide was successfully prepared,and improved anti-inflammation effects in mice suggests that the developed preparation has better bioavailability.In this study,we first determined the solubility of andrographolide in different excipients and found that ome oils（camellia oil and isopropyl myristate（IPM））,and surfactants（Tween 20,Tween 80,PEG600MO and Labrasol）,and co-surfactants（TRANSCUTOL V and PEG400）showed better solubility for andrographolide.Next,the oil phase（camellia oil,IPM）and surfactants（Tween 20,Tween 80,PEG600MO,Labrasol）were investigated for their compatibility by preparing blank microemulsion and evaluating its appearance and emulsification state.According to the results of the compatibility test,camellia oil,PEG600MO and Labrasol,PEG400 and TRANSCUTOL V were choosen as oil phase,surfactants and co-surfactants,respectively,to screen optimized prescription by the pseudo-ternary phase diagram.The optimum prescription was comprised by 10%camellia as the oil phase,PEG600MO as the surfactant,PEG400 as the co-surfactants（PEG600MO/PEG400=1）,and the hihest andrographolide loading was 4.5%.The optimal formulation of andrographolide microemulsion showed a pale yellow transparent liquid.The particle size of microemulsion ranged from 8 to 20 nm.Parameters including appearance,particle size and drug content were used as assessment criterias for the emulsion,and the developed andrographolide microemulsion showed ideal stability.In this study,a HPLC method for the analysis of andrographolide was established.Good linear relationship was obtained for the analysis of andrographolide in the range of7.81～250μg/m L（R²=0.9995）.The average recoveries for low,medium and high concentrations of drugs（7.81μg/m L,125μg/m L,250μg/m L）were 92.0%,103.9%,and 99.2%,respectively.The RSD for the analysis of and rographolide（125μg/m L）within 24 hours was 2.10%,which indicated good stability.The developed HPLC method for andrographolide analysis is suitable for the determination of andrographolide in microemulsion with characters of simplity,high specificity,accuracy and efficiency.The safety of andrographolide microemulsion was evaluated by acute toxicity assy in mice.Results showed that gavage administration of 200 mg/kg/d and 400 mg/kg/d of andrographolide microemulsion did not no change appearance,behavior and body weight of mice,compared to the control group.At day 7 post andrographolide microemulsion administration,no systemic poisoning and death were observed,and breathing,and limb activities were also not affected.In vivo inflammation model induced by LPS was established to investigate the therapeutic effects of andrographolide microemulsion.The results showed that 100 mg/kg/d of andrographolide microemulsion significantly protected LPS-induced mice with a 50% survival,while 100 mg/kg/d of andrographolide suspension showed a lower protection on LPS-induced mice（30%）.This result suggested that the bioavailability of andrographolide microemulsion was better than that of andrographolide suspension.