No abstract

In this study we designed and synthesized several heptapeptides that are enforced to form an amphipathic helix using all-hydrocarbon stapling system and evaluated their antimicrobial and hemolytic activities. The antimicrobial activity showed clear structure-activity relationships, confirming the importance of helicity and amphipathicity. Some stapled heptapeptides displayed a moderate antimicrobial activity along with a low hemolytic activity. To our best knowledge, although not highly potent, these stapled peptides represent the shortest helical amphipathic antimicrobial peptides reported to date. The preliminary data obtained in this work would serve as a good starting point for further developing short analogs of amphipathic helical antimicrobial peptides.

Ocimum gratissimum L. is a fragrant plant of the Lamiaceae family. O. gratissimum has been used in folk medicine, cosmetics, and food industry. In this study, herbs of O. gratissimum were collected in the summer in Northern Vietnam and extracted for essential oils by hydrodistillation, followed by gas chromatography - mass spectrometry (GC-MS) analysis. The efficiency of essential oil extraction was 0.2258% ± 0.0735. According to the analysis results, twenty-seven components were identified. The main ingredients include Eugenol (65.135%), Ocimene <(Z) -b-> (7.20%), Caryophyllene <E-> (6.64%), and Germacrene D (12.03%). This result suggests that the O. gratissimum essential oil is a potential source of antimicrobial, preservative and flavoring agent.

In our previous study, we showcased the potential of an all‐hydrocarbon stapled heptapeptide as a privileged scaffold for the design of artificial antimicrobial peptides. We demonstrated that the amphipathic helicity and the subtle balance between hydrophobicity and hydrophilicity are important structural features for the antimicrobial activities of this class of antimicrobial agents. In this study, we show that elimination of the N‐acetyl cap can further improve the pharmacological properties of the most potent stapled heptapeptides. The structure–activity relationships newly established in this study would serve as a critical asset for the further development of a new class of antimicrobial agents to combat the rising problem of antibiotic resistance.

The essential oils from leaves and twigs of Magnolia hookeri var. longirostrata D.X.Li & R.Z.Zhou and Magnolia insignis Wall., growing wild in Ha Giang Province of Vietnam, were obtained by hydrodistillation and analyzed by gas chromatography-flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The respective yields of the M. hookeri var. longirostrata leaf and twig oils were 0.14% and 0.05% (v/w), and of the M. insignis leaf and twig oils were 0.16% and 0.05% (v/w), calculated on a dry weight basis. Major components of the oils of M. hookeri var. longirostrata were: Linalool (21.3%), (E)-nerolidol (12.2%) and neo-intermedeol (13.5%) (leaf oil); 1,8-cineole (13.3%) and linalool (17.1%) (twig oil). Major components of the oils of M. insignis were: Linalool (24.1%), geraniol (14.9%) and (E)-nerolidol (22.5%) (leaf oil); 1,8-cineole (9.5%) and linalool (26.9%) (twig oil). The essential oils from M. insignis showed stronger inhibitory effects on the seven test microorganisms than those from M. hookeri var. longirostrata. Candida albicans and Lactobacillus fermentum were more sensitive to the essential oils than the other tested microorganisms. This is the first time information on essential oils of M. hookeri var. longirostrata leaves and twigs and of M. insignis twigs are reported.