Arginine and tryptophan-rich dendritic antimicrobial peptides that disrupt membranes for bacterial infection in vivo.

The potent antibacterial activity and low resistance of antimicrobial peptides (AMPs) render them potential candidates for treating multidrug-resistant bacterial infections. Herein, a minimalist design strategy was proposed employing the "golden partner" combination of arginine (R) and tryptophan (W), along with a dendritic structure to design AMPs. By extension, the α/ε-amino group and the carboxyl group of lysine (K) were utilized to link R and W, forming dendritic peptide templates αRn(εRn)KWm-NH2 and αWn(εWn)KRm-NH2, respectively. The corresponding linear peptide templates R2nKWm-NH2 and W2nKRm-NH2 were used as controls. Their physicochemical properties, activity, toxicity, and stability were compared. Among these new peptides, the dendritic peptide R2(R2)KW4 was screened as a prospective candidate owing to its preferable antibacterial properties, biocompatibility, and stability. Additionally, R2(R2)KW4 not only effectively restrained the progression of antibiotic resistance, but also demonstrated synergistic utility when combined with conventional antibiotics due to its unique membrane-disruptive mechanism. Furthermore, R2(R2)KW4 possessed low toxicity (LD50 = 109.31 mg/kg) in vivo, while efficiently clearing E. coli in pulmonary-infected mice. In conclusion, R2(R2)KW4 has the potential to become an antimicrobial regent or adjuvant, and the minimalist design strategy of dendritic peptides provides innovative and encouraging thoughts in designing AMPs.

Rational design of a new short anticancer peptide with good potential for cancer treatment.

Anticancer peptides (ACPs) have regarded as a new generation of promising antitumor drugs due to the unique mode of action. The main challenge is to develop potential anticancer peptides with satisfied antitumor activity and low toxicity. Here, a series of new α-helical anticancer peptides were designed and synthesized based on the regular repeat motif KLLK. The optimal peptides 14E and 14Aad were successfully derived from the new short α-helical peptide KL-8. Our results demonstrated that 14E and 14Aad had good antitumor activity and low toxicity, exhibiting excellent selectivity index. This result highlighted that the desirable modification position and appropriate hydrophobic side-chain structure of acidic amino acids played critical roles in regulating the antitumor activity/toxicity of new peptides. Further studies indicated that they could induce tumor cell death via the multiple actions of efficient membrane disruption and intracellular mechanisms, displaying apparent superiority in combination with PTX. In addition, the new peptides 14E and 14Aad showed excellent antitumor efficacy in vivo and low toxicity in mice compared to KL-8 and PTX. Particularly, 14Aad with the longer side chain at the 14th site exhibited the best therapeutic performance. In conclusion, our work provided a new avenue to develop promising anticancer peptides with good selectivity for tumor therapy.

Novel ß-Hairpin Antimicrobial Peptide Containing the ß-Turn Sequence of -NG- and the Tryptophan Zippers Facilitate Self-Assembly into Nanofibers, Exhibiting Excellent Antimicrobial Performance.

Antimicrobial peptides (AMPs) have emerged as promising agents to combat the antibiotic resistance crisis due to their rapid bactericidal activity and low propensity for drug resistance. However, AMPs face challenges in terms of balancing enhanced antimicrobial efficacy with increased toxicity during modification processes. In this study, de novo d-type ß-hairpin AMPs are designed. The conformational transformation of self-assembling peptide W-4 in the environment of the bacterial membrane and the erythrocyte membrane affected its antibacterial activity and hemolytic activity and finally showed a high antibacterial effect and low toxicity. Furthermore, W-4 displays remarkable stability, minimal occurrence of drug resistance, and synergistic effects when combined with antibiotics. The in vivo studies confirm its high safety and potent wound-healing properties at the sites infected by bacteria. This study substantiates that nanostructured AMPs possess enhanced biocompatibility. These advances reveal the superiority of self-assembled AMPs and contribute to the development of nanoantibacterial materials.

A novel antimicrobial peptide with broad-spectrum and exceptional stability derived from the natural peptide Brevicidine.

The global issue of antibiotic resistance is increasingly severe, highlighting the urgent necessity for the development of new antibiotics. Brevicidine, a natural cyclic lipopeptide, exhibits remarkable antimicrobial activity against Gram-negative bacteria. In this study, a comprehensive structure-activity relationship of Brevicidine was investigated through 20 newly synthesized cyclic lipopeptide analogs, resulting in the identification of an optimal linear analog 22. The sequence of analog 22 consisted of five d-amino acids and four non-natural amino acid 2,5-diaminovaleric acid (Orn) and conjugated with decanoic acid at N-terminal. Compared to Brevicidine, analog 22 was easier to synthesize, and exerted broad spectrum antimicrobial activity and excellent stability (t1/2 = 40.98 h). Additionally, analog 22 demonstrated a rapid bactericidal effect by permeating non-specifically through the bacterial membranes, thereby minimizing the likelihood of inducing resistance. Moreover, it exhibited remarkable efficacy in combating bacterial biofilms and reversing bacterial resistance to conventional antibiotics. Furthermore, it effectively suppressed the growth of bacteria in vital organs of mice infected with S. aureus ATCC 25923. In conclusion, analog 22 may represent a potential antimicrobial peptide for further optimization.

Structure modification of anoplin for fighting resistant bacteria.

The emergence of bacterial resistance has posed a significant challenge to clinical antimicrobial treatment, rendering commonly used antibiotics ineffective. The development of novel antimicrobial agents and strategies is imperative for the treatment of resistant bacterial infections. Antimicrobial peptides (AMPs) are considered a promising class of antimicrobial agents due to their low propensity for resistance and broad-spectrum activity. Anoplin is a small linear α-helical natural antimicrobial peptide that was isolated from the venom of the solitary wasp Anplius samariensis. It exhibits rich biological activity, particularly broad-spectrum antimicrobial activity and low hemolytic activity. Over the past three decades, more than 40 research publications on anoplin have been made available online. This review focuses on the advancements of anoplin in antimicrobial research, encompassing its sources, characterization, antimicrobial activity, influencing factors and structural modifications. The aim is to provide assistances for the development of new antimicrobial agents that can combat bacterial resistance.

Structure-Activity Relationship Study of Antimicrobial Peptide PE2 Delivered Novel Linear Derivatives with Potential of Eradicating Biofilms and Low Incidence of Drug Resistance.

The ongoing emergence of antibiotic-resistant pathogens had been dramatically stimulating and accelerating the need for new drugs. PE2 is a kind of cyclic lipopeptide with broad-spectrum antimicrobial activity. Herein, its structure-activity relationship was systematically investigated by employing 4 cyclic analogues and 23 linear analogues for the first time. The screened linear analogues 26 and 27 bearing different fatty acyls at N-termini and a Tyr residue at the 9th position had superior potency compared to the cyclic analogues and showed equivalent antimicrobial activity compared with PE2. Notably, 26 and 27 exhibited significant ability against multidrug-resistant bacteria, favorable resistance to protease, excellent performance against biofilm, low drug resistance, and high effectiveness against the mice pneumonia model. The antibacterial mechanisms of PE2 and linear derivatives 26 and 27 were also preliminarily explored in this study. As described above, 26 and 27 are promising antimicrobial candidates for the treatment of infections associated with drug-resistant bacteria.

One New Acid-Activated Hybrid Anticancer Peptide by Coupling with a Desirable pH-Sensitive Anionic Partner Peptide.

Anticancer peptides (ACPs) are promising antitumor resources, and developing acid-activated ACPs as more effective and selective antitumor drugs would represent new progress in cancer therapy. In this study, we designed a new class of acid-activated hybrid peptides LK-LE by altering the charge shielding position of the anionic binding partner LE based on the cationic ACP LK and investigated their pH response, cytotoxic activity, and serum stability, in hoping to achieve a desirable acid-activatable ACP. As expected, the obtained hybrid peptides could be activated and exhibit a remarkable antitumor activity by rapid membrane disruption at acidic pH, whereas its killing activity could be alleviated at normal pH, showing a significant pH response compared with LK. Importantly, this study found that the peptide LK-LE3 with the charge shielding in the N-terminal of LK displayed notably low cytotoxicity and more stability, demonstrating that the position of charge masking is extremely important for the improvement of peptide toxicity and stability. In short, our work opens a new avenue to design promising acid-activated ACPs as potential targeting agents for cancer treatment.

Short, mirror-symmetric antimicrobial peptides centered on "RRR" have broad-spectrum antibacterial activity with low drug resistance and toxicity.

The increasingly severe bacterial resistance worldwide pushes people to discover and design potential antibacterial drugs unavoidably. In this work, a series of short, mirror-symmetric peptides were designed and successfully synthesized, centered on "RRR" and labeled with hydrophobic amino acids at both ends. Based on the structure-activity relationship analysis, LWWR (LWWRRRWWL-NH2) was screened as a desirable mirror-symmetric peptide for further study. As expected, LWWR displayed broad-spectrum antibacterial activity against the standard bacteria and antibiotic-resistant strains. Undoubtedly, the high stability of LWWR in a complex physiological environment was an essential guarantee to maximizing its antibacterial activity. Indeed, LWWR also exhibited a rapid bactericidal speed and a low tendency to develop bacterial resistance, based on the multiple actions of non-receptor-mediated membrane actions and intra-cellular mechanisms. Surprisingly, although LWWR showed similar in vivo antibacterial activity compared with Polymyxin B and Melittin, the in vivo safety of LWWR was far higher than that of them, so LWWR had better therapeutic potential. In summary, the desirable mirror-symmetric peptide LWWR was promised as a potential antibacterial agent to confront the antibiotics resistance crisis. STATEMENT OF SIGNIFICANCE: Witnessing the growing problem of antibiotic resistance, a series of short, mirror-symmetric peptides based on the symmetric center "RRR" and hydrophobic terminals were designed and synthesized in this study. Among, LWWR (LWWRRRWWL-NH2) presented broad-spectrum antibacterial activity both in vitro and in vivo due to its multiple mechanisms and good stability. Meanwhile, the low drug resistance and toxicity of LWWR also suggested its potential for clinical application. The findings of this study will provide some inspiration for the design and development of potential antibacterial agents, and contribute to the elimination of bacterial infections worldwide as soon as possible.

Improving the Antimicrobial Performance of Amphiphilic Cationic Antimicrobial Peptides Using Glutamic Acid Full-Scan and Positive Charge Compensation Strategies.

Nonselective toxicity of antimicrobial peptides (AMPs) needs to be solved urgently for their application. Temporin-PE (T-PE, FLPIVAKLLSGLL-NH2), an AMP extracted from skin secretions of frogs, has high toxicity and specific antimicrobial activity against Gram-positive bacteria. To improve the antimicrobial performance of T-PE, a series of T-PE analogues were designed and synthesized by glutamic acid full-scan, and then their key positions were replaced with lysine. Finally, E11K4K10, the highest therapeutic indicial AMP, was screened out. E11K4K10 was not easy to induce and produce drug-resistant bacteria when used alone, as well as it could also inhibit the development of the drug resistance of traditional antibiotics when it was used in combination with the traditional antibiotics. In addition, E11K4K10 had an excellent therapeutic effect on a mouse model of pulmonary bacterial infection. Taken together, this study provides a new approach for the further improvement of new antimicrobial peptides against the antimicrobial-resistance crisis.

Constructing new acid-activated anticancer peptide by attaching a desirable anionic binding partner peptide.

Improving the cell selectivity of anticancer peptides (ACPs) is a major hurdle in their clinical utilisation. In this study, a new acid-activated ACP was designed by conjugating a cationic ACP LK to its anionic binding partner peptide (LEH) via a disulphide linker to trigger antitumor activity at acidic pH while masking its killing activity at normal pH. Three anionic binding peptides containing different numbers of glutamic acid (Glu) and histidine were engineered to obtain an efficient acid-activated ACP. The conjugates LK-LEH2 and LK-LEH3 exhibited 6.1- and 8.0-fold higher killing activity at pH 6.0 relative to at pH 7.4, respectively, suggesting their excellent pH-dependent antitumor activity; and their cytotoxicity was 10-fold lower than that of LK. However, LK-LEH4 had no pH-responsive killing effect. Interestingly, increasing the number of Glu from 2 to 4 increased the pH-response of the physical mixture of LK and LEH; conversely, they weakly decreased the cytotoxicity of LK, suggesting that the conjugate connection is required to achieve excellent pH dependence while maintaining minimum toxicity. LK-LEH2 and LK-LEH3 were more enzymatically stable than LK, indicating their potential for in vivo application. Our work provided a basis for designing promising ACPs with good selectivity and low toxicity.

Novel synovial targeting peptide-sinomenine conjugates as a potential strategy for the treatment of rheumatoid arthritis.

Sinomenine (SIN) is an effective anti-inflammatory agent, but its therapeutic efficacy is limited by its short half-life and the high dosage required. Tissue-specific strategies have the potential to overcome these limitations. The synovial homing peptide (CKSTHDRLC) was identified to have high synovial endothelium targeting affinity. In this work, two peptide-drug conjugates (PDCs), conjugate (L) and conjugate (C), were synthesized, in which SIN was covalently connected to the linear and cyclic synovial homing peptide, respectively, via a 6-aminocaproic acid linker. An evaluation of biostability showed that conjugate (C) was more stable in mouse serum and inflammatory joint homogenate than conjugate (L). The two conjugates gradually released free SIN. Interestingly, conjugate (L) self-cyclized via a disulfide bridge in a biological environment, which significantly impacted its biostability. It had an almost equipotent half-life in serum but faster degradation in the inflammatory joint than conjugate (C). Therefore, conjugate (C) exhibited better therapeutic efficacy and tissue targeting. All the results indicated that PDCs particularly in its cyclic form might be more efficient for targeted deliver and represent a potential strategy for the treatment of rheumatoid arthritis.

Novel ß-Hairpin Antimicrobial Peptides Containing the ß-Turn Sequence of -RRRF- Having High Cell Selectivity and Low Incidence of Drug Resistance.

The emergence of multidrug-resistant bacteria has dramatically increased the lethality, level of resistance, and difficulty of treatment. In this study, a series of new antimicrobial peptides (AMPs) based on the ß-hairpin structure with the template (XY)2RRRF(YX)2-NH2 (X: hydrophobic amino acids; Y: cationic amino acids) were synthesized; surprisingly, almost all of the new peptides have strong antibacterial activity and negligible hemolytic toxicity. Particularly, the therapeutic index (TI) values of F(RI)2R and F(KW)2K reached up to 115.9 and 70.7, respectively. In addition, they did not show induced drug resistance and inhibited the development of antibiotic resistance when combined and used with traditional antibiotics. In addition, their antibacterial mechanism was preliminarily studied. Moreover, the new peptides F(RI)2R and F(KW)2K showed excellent performance in the pulmonary bacterial infection model and low toxicity in mice. In conclusion, F(RI)2R and F(KW)2K are considered new antimicrobial alternatives to address the antimicrobial-resistance crisis.

Tuning the Activity of Anoplin by Dendrimerization of Lysine and Lipidation of the N-Terminal.

Dendrimeric antimicrobial peptides or lipopeptides have strong transmembrane ability and antibacterial activity. To obtain some ideal antimicrobial peptides, anoplin, a natural antimicrobial peptide with weak antimicrobial activity, was modified by C-terminal dendrimerization using lysine and N-terminal lipidation using fatty acids. 2K-3A-C4, a trimer of anoplin, was dendrimerized by two lysines at the C-terminal and was lipidated by n-butyric acid at the N-terminal, and thus exhibited the best antibacterial activity. However, the trimer had high hemolytic activity. Finally, A-C8, a simple structural lipopeptide, which is not a dendrimer, was obtained following the lipidation of anoplin using octanoic acid; it exhibited the highest therapeutic index, which makes it a probable antibiotic and thus was screened out.

Novel Broad-Spectrum Antimicrobial Peptide Derived from Anoplin and Its Activity on Bacterial Pneumonia in Mice.

The emergence of multidrug-resistant bacteria has major issues for treating bacterial pneumonia. Currently, anoplin (GLLKRIKTLL-NH2) is a natural antimicrobial candidate derived from wasp venom. In this study, a series of new antimicrobial peptide (AMP) anoplin analogues were designed and synthesized. The relationship between their biological activities and their positive charge, hydrophobicity, amphipathicity, and secondary structure are described. The characteristic shared by these peptides is that positively charged amino acids and hydrophobic amino acids are severally arranged on the hydrophilic and hydrophobic surface of the α-helix to form a completely amphiphilic structure. To achieve ideal AMPs, below the range of the threshold of the cytotoxicity and hemolytic activity, their charges and hydrophobicity were increased as much. Among the new analogues, A-21 (KWWKKWKKWW-NH2) exhibited the greatest antimicrobial activity (geometric mean of minimum inhibitory concentrations = 4.76 µM) against all the tested bacterial strains, high bacterial cell selectivity in vitro, high effectiveness against bacterial pneumonia in mice infected with Klebsiella pneumoniae, and low toxicity in mice (LD50 = 82.01 mg/kg). A-21 exhibited a potent bacterial membrane-damaging mechanism and lipopolysaccharide-binding ability. These data provide evidence that A-21 is a promising antimicrobial candidate for the treatment of bacterial pneumonia.

New Antimicrobial Peptides with Repeating Unit against Multidrug-Resistant Bacteria.

With the aim of tackling the increasingly serious antimicrobial resistance and improving the clinical potential of AMPs, a facile de novo strategy was adopted in this study, and a series of new peptides comprising repeating unit (WRX)n (X represents I, L, F, W, and K; n = 2, 3, 4, or 5) and amidation at C-terminus were designed. Most of the newly designed peptides exhibited a broad range of excellent antimicrobial activities against various bacteria, especially difficult-to-kill multidrug-resistant bacteria clinical isolates. Among (WRK)4 and (WRK)5, with n = 4 and n = 5 of repeating unit WRK, the highest selectivity for anionic bacterial membranes over a zwitterionic mammalian cell membrane is presented with strong antimicrobial potential and low toxicity. Additionally, both (WRK)4 and (WRK)5 emerged with fast killing speed and low tendency of resistance in sharp contrast to the conventional antibiotics ciprofloxacin, gentamicin, and imipenem, as well as having antimicrobial activity through multiple mechanisms including a membrane-disruptive mechanism and an intramolecular mechanism (nucleic acid leakage, DNA binding and ROS generation) characterized by a series of assays. Furthermore, (WRK)4 exerted impressive therapeutic effects in vivo similarly to polymyxin B but displayed much lower toxicity in vivo than polymyxin B. Taken together, the newly designed peptides (WRK)4 and (WRK)5 presented tremendous potential as novel antimicrobial candidates in response to the growing antimicrobial resistance.

Antimicrobial peptides with symmetric structures against multidrug-resistant bacteria while alleviating antimicrobial resistance.

In response to the dramatically increasing antimicrobial resistance, a series of new symmetric peptides were designed and synthesized in this study by a "WWW" motif as the symmetric center, arginine as the positive charge amino acid and the terminus symmetrically tagged with hydrophobic amino acids. Amongst the new symmetric peptide FRRW (FRRWWWRRF-NH2) presented the highest cell selectivity for bacteria over mammalian cell and exerted excellent antimicrobial potential against a broad of bacteria, especially difficult-to-kill multidrug-resistant strains clinical isolates. FRRW also displayed perfect stability in physiological salt ions and rapid killing speed as well as acted on multiple mechanisms including non-receptor mediated membrane and intra-molecular mechanisms. Importantly, FRRW emerged a low tendency of resistance in contrast to traditional antibiotics ciprofloxacin and gentamicin. What's more, FRRW could resist or alleviate or even reverse the ciprofloxacin- and gentamicin-resistance by changing the permeability of bacterial membrane and inhibiting the efflux pumps of bacteria. Furthermore, FRRW exhibited remarkable effectiveness and higher safety in vivo than polymyxin B. In summary, the new symmetric peptide FRRW was promised to be as a new antimicrobial candidate for overcoming the increasing bacterial resistance.

Ultra-short lipopeptides against gram-positive bacteria while alleviating antimicrobial resistance.

Facing the continuously urgent demands for novel antimicrobial agents since the growing emergence of bacterial resistance, a series of new ultra-short lipopeptides, composed of tryptophan and arginine and fatty acids, were de novo designed and synthesized in this study. Most of the new lipopeptides exhibited preferable antimicrobial potential against gram-positive bacteria, including MRSA clinical isolates. Among them, the new lipopeptides C14-R1 (C14-RWW-NH2) and C12-R2 (C12-RRW-NH2) presented higher selectivity to bacterial membranes over mammalian membranes and low cytotoxicity, which also maintained better antimicrobial activity in the presence of physiological salts or serum. Most importantly, C14-R1 and C12-R2 not only expressed low tendency of bacterial resistance, but also displayed synergistic antimicrobial activity against antibiotics-resistant bacteria when be used in combination with antibiotics. Especially, they could alleviate or reverse the ciprofloxacin resistance, implying an ideal anti-resistance function. Moreover, the new lipopeptides showed rapid killing kinetics, obvious effectiveness for persistent cells that escaped from antibiotics, and strong anti-biofilm ability, which further indicated a preferable anti-resistance ability. The typical non-receptor-mediated membrane mechanisms were characterized by LPS/LTA competitive inhibition, cytoplasmic membrane depolarization, PI uptake assay and scanning electron microscopy analyses systematically. Reactive oxygen species (ROS) generation assays supplemented their intracellular targets in the meanwhile. In addition to the remarkable antimicrobial activity in vivo, the new lipopeptides also displayed significant anti-inflammatory effect in vivo. To sum up, the new lipopeptides C14-R1 and C12-R2 viewed as novel antimicrobial alternatives for tackling the impending crisis of antimicrobial resistance.

New designed pH-responsive histidine-rich peptides with antitumor activity.

Anticancer peptides have received widespread attention as alternative antitumor therapeutics due to their unique action mode. However, the systemic toxicity hampers their successful utilisation in tumour therapy. Here, the tumour acidic environment was used as a trigger to design a series of histidine-rich peptides by optimising the distribution of histidine and leucine based on the amphiphilic peptide LK, in hoping to achieve desirable acid-activate anticancer peptides. Among all the obtained peptides, L9H5-1 showed enhanced antitumor activity at acidic pH concomitant with low toxicity at normal pH, exhibiting excellent pH-response. At acidic pH, protonated L9H5-1 could rapidly kill tumour cells by efficient membrane disruption as evidenced by in vitro experiments, including increasing intracellular PI uptake and LDH release, dramatic membrane damage and increase of later apoptotic/necrotic cells. Moreover, no cell cycle arrest was observed after treated with L9H5-1. Interestingly, this study found that the new peptides with the same number of histidines and leucines displayed different pH-dependent antitumor activity, indicating that the position of amino acid alteration is extremely important for the design of acid-activated histidine-rich peptides. In short, our work provides a new avenue to develop new acid-activated anticancer peptides as promising antitumor drugs with high efficiency and good selectivity.

Newly designed antimicrobial peptides with potent bioactivity and enhanced cell selectivity prevent and reverse rifampin resistance in Gram-negative bacteria.

The increasing prevalence of antibiotic resistance in Gram-negative bacteria calls for the discovery of novel effective therapeutic strategies urgently. Mastoparan-C (MP-C), a typical cationic α-helical antimicrobial peptide, possesses remarkable broad-spectrum antimicrobial activity. However, its high cytotoxicity toward normal mammalian cells precludes it for further development. In this study, to avoid non-specific membrane lysis and investigate the structure-function relationships of each amino acid of MP-C, a series of new MP-C analogs were rationally designed by amino acid substitution and peptide truncation. Three potential newly designed peptides L1G, L7A, and L1GA5K with excellent bioactivity, modest cell toxicity, low resistance tendency, and moderate stability to physiological salts and proteases were screened out. Moreover, the newly designed peptides showed synergy or additive effects against Gram-negative bacteria, when they combined with conventional antibiotics gentamicin, rifampin, and polymyxin B. The results from the time-kill kinetics, outer/inner membrane permeabilization, scanning electron microscope (SEM), and flow cytometry demonstrated that the newly designed peptides could kill bacteria rapidly by membrane destruction and intracellular contents leakage in a concentration and time-dependent manner. Specifically, the most cell-selective peptide L1GA5K exhibited potent antimicrobial activity against rifampin-resistant E. coli (RRE) and prevented the emergence of rifampin resistance in Enterobacter. Besides, L1GA5K was capable of reversing rifampin resistance in RRE through the outer membrane permeabilization when used in combination with rifampin. Collectively, our results suggested that the newly designed peptides are hopeful antibiotic alternatives, and the usage of them as an adjuvant to prevent and reverse antibiotic resistance is a promising strategy for tackling the risk of drug-resistant Gram-negative bacteria.

Hepatoprotective effect of total flavonoids from Glycyrrhiza uralensis Fisch in liver injury mice.

This work aimed to investigate the hepatoprotective effect of total flavonoids from Glycyrrhiza uralensis. The main compounds in licorice total flavonoids (LTF) were isolated from Glycyrrhiza uralensis and their total content in LTF were more than 60%. Hepatoprotective effects of LTF were investigated in three kinds of hepatic injury mice model induced by high-fat emulsion, Chinese liquor and tetrachloromethane. Serum ALT, AST and ALP levels and hepatic MDA, TG, cholesterol, and hydroxyproline of hepatic injury mice were reduced by LTF. Simultaneously, hepatic SOD and glutathione were increased by LTF. These results suggested that LTF can repair liver tissue and reduce hepatic injury via alleviating inflammation, improving antioxidant enzyme activity and reducing oxidative stress in liver tissue and it may be a valuable natural source of hepatoprotective activity.