Overall assessment of antimicrobial peptides in piglets: a set of meta-analyses.

Developing alternatives to antibiotics is an urgent need in livestock production. Antimicrobial peptides (AMPs) are regarded as powerful antibiotic substitutes (ASs) because AMPs have broad-spectrum antimicrobial activities and growth-promoting ability. Here, we aimed to comprehensively assess the effects of AMPs on the growth performance, diarrhea rate, intestinal morphology and immunity of healthy or challenged piglets, compared with an antibiotics group or negative control group. We performed a set of meta-analyses of feeding trials from database inception to 27 May 2019. Among the 1379 identified studies, 20 were included in our meta-analyses (56 arms and 4067 piglets). The meta-analyses revealed that (1) compared with the negative control group, AMPs significantly improved the healthy piglets' average daily gain (ADG), average daily feed intake (ADFI), gain : feed ratio (G/F), levels of immune globulin (Ig) IgM and IgG, and intestinal villus height : crypt depth ratio (V/C) (P < 0.05). Meanwhile, AMPs significantly increased the challenged piglets' ADG, ADFI, G/F and V/C of the jejunum and ileum, and notably deceased the diarrhea rate (P < 0.05); (2) compared with antibiotics group, the effects of AMPs were slightly weaker than those of antibiotics in the healthy piglets, but AMPs have similar effects to those of antibiotics in challenged piglets. In a higher purity, the optimal dose of AMPs may be approximately 0.01%. Our findings indicate that AMPs can improve piglet growth performance, enhance immunity, benefit intestinal morphology and decrease the diarrheal rate. AMPs could be great ASs especially under infection conditions.

Enhancement of antibacterial activity of tilmicosin against Staphylococcus aureus by solid lipid nanoparticles in vitro and in vivo.

This study aimed to enhance the antibacterial activity of tilmicosin by solid lipid nanoparticles (SLN). Tilmicosin-loaded hydrogenated castor oil (HCO)-SLN was prepared using a hot homogenisation and ultrasonication method. The physicochemical characteristics of SLN were investigated by scanning electron microscopy (SEM) and photon correlation spectroscopy (PCS). The antibacterial activity of tilmicosin-SLN against Staphylococcus aureus was evaluated by growth inhibition and colony-counting method. A therapeutic study of tilmicosin-SLN was conducted by subcutaneous injection in a mouse mastitis model infected with S. aureus by teat canal infusion. Therapeutic efficacy was assessed by physical appearance of the mammary gland and measurement of colony-forming units (CFU) per gland. The results showed that the diameter, polydispersivity index, zeta potential, encapsulation efficiency and loading capacity of the nanoparticles were 343±26 nm, 0.33±0.08, -7.9±0.4 mV, 60.4±3.3% and 11.2±0.47%, respectively. Tilmicosin-SLN showed a sustained-release effect and sustained and enhanced antibacterial activity in vitro. SLN significantly enhanced the therapeutic efficacy of tilmicosin determined by lower CFU counts and a decreased degree of inflammation. These results demonstrated that the HCO-SLN is an effective carrier to enhance the antibacterial activity of tilmicosin.

Effects of poly (lactic-co-glycolic acid) as a co-emulsifier on the preparation and hypoglycaemic activity of insulin-loaded solid lipid nanoparticles.

Poly (lactic-co-glycolic acid) (PLGA) was used as a co-emulsifier in the preparation of insulin-loaded solid lipid nanoparticles (SLN) with hydrogenated castor oil as lipid matrix and lecithin as surfactant by double-emulsion technique. The effects of PLGA on the preparation and hypoglycaemic activity of insulin-loaded SLN were studied. The results showed that with the supplement of PLGA, the encapsulation efficiency and loading capacity were increased significantly from 79.08 +/- 1.62 to 85.57 +/- 3.21% and 1.58 +/- 0.03 to 1.71 +/- 0.06%, whereas the surface charge and particle size were changed insignificantly from -25.87 +/- 2.65 to -22.67 +/- 1.19 mv and 431.0 +/- 16.1 to 397.0 +/- 68.0 nm, respectively. In vivo studies demonstrated that PLGA increased the sustained hypoglycaemic activity from 12 to 36 h and 24 to 120 h in normal and steptozotocin-induced diabetic mice after a single intramuscular injection of the insulin-loaded SLN. These results demonstrated that PLGA could enhance the entrapment of insulin in the nanoparticles, and more importantly, prolong the time of hypoglycaemic activity of the insulin-loaded SLN.

Stereoselective total synthesis of chrysanthemol.

Chrysanthemol (1), a trans-eudesmane type sesquiterpene from Chrysanthemum indicum L., possesses certain anti-inflammatory activity. Its total synthesis was approached from two alternative routes and finally accomplished in ten steps from R-(+)-carvone via alpha-eudesmol (10) as the key intermediate. The overall yield is 2.4% and the spectral data of the synthetic target compound were identical with that of natural chrysanthemol (1). Seven intermediary compounds were tested for inhibitory effects on the carragenan-induced swelling of mouse paw but demonstrated no obvious activities.