Abstract:Presently the search for new drugs from natural resources is of growing interest to the pharmaceutical industry. Natural products have been the source of new drugs since ancient times. Plants are a good source of secondary metabolites which have been found to have beneficial properties. The present study is a review of the chemistry and pharmacology of Citrus sinensis. This review reveals the therapeutic potential of C. sinensis as a source of natural compounds with important activities that are beneficial for human health that could be used to develop new drugs.

Three lignans and four flavonoids were isolated and characterized from Larrea tridentata and compounds were tested against 16 bacterial species/strains. Results showed that: dihydroguaiaretic acid (1) had activity towards methicillin resistant (MR) Staphylococcus aureus (minimum inhibitory concentration (MIC) 50 µg/mL) and multidrug-resistant (MDR) strains of Mycobacterium tuberculosis (MIC 12.5-50 µg/mL); 4-epi-larreatricin (2) was active against Enterobacter cloacae (MIC 12.5 µg/mL), as well as sensitive (MIC 50 µg/mL) and MDR strains of M. tuberculosis (MIC 25 µg/mL). 3'-Demethoxy-6-O-demethylisoguaiacin (3) displayed activity against sensitive and resistant S. aureus (MIC 25 µg/mL), Enterococcus faecalis (MIC 12.5 µg/mL), Escherichia coli (MIC 50 µg/mL), E. cloacae (MIC 12.5 µg/mL) and MDR strains of M. tuberculosis (MIC 12.5 µg/mL). 5,4'-Dihydroxy-3,7,8,3'-tetramethoxyflavone (4) and 5,4'-dihydroxy-3,7,8-trimethoxyflavone (5) were active against M. tuberculosis MDR strains having MIC values of 25 and 25-50 µg/mL, respectively, while 5,4'-dihydroxy-7-methoxyflavone (6) was active against S. aureus (MIC 50 µg/mL) and E. faecalis (MIC 50 µg/mL). We concluded that lignan 3 is the main compound responsible for the antibacterial activity of L. tridentata. Lignans 1 and 2 as well as flavonoid 6 contribute with some degree of antibacterial activity. On the other hand, compounds 1, 2, 3, 4 and 5 contributed to the antimycobacterial activity found in L. tridentata.

Bioassay guided fractionation of an antimycobacterial extract of Foeniculum vulgare var dulce (Apiaceae) led to the isolation and characterization of 5-hydroxyfurano-coumarin. The chemical structure of this compound was elucidated by 1 H and 13 C (1D and 2D) Nuclear Magnetic Resonance (NMR) spectroscopy. In addition, the active fractions were analyzed by GC-MS and seventy eight compounds were identified; the major compounds were 1,3-benzenediol, 1-methoxycyclohexene, o -cymene, sorbic acid, 2-hydroxy-3-methyl-2-cyclopenten-1-one, estragole, limonene-10-ol and 3-methyl-2-cyclopenten-1-one. Twenty compounds identified in the active fractions were tested against one sensitive and three MDR strains of Mycobacterium tuberculosis using the Alamar Blue microassay. Compounds that showed some degree of antimycobacterial activity against all strains tested were the following: linoleic acid (MIC 100 µg/mL), oleic acid (MIC 100 µg/mL), 1,3-benzenediol (MIC 100–200 µg/mL), undecanal (MIC 50–200 µg/mL), and 2,4-undecadienal (MIC 25–50 µg/mL), the last being the most active compound. To our knowledge, this is the first report of the presence of 5-hydroxy-furanocoumarin in F. vulgare .

Bacterial infections represent one of the main threats to global public health. One of the major causative agents associated with high morbidity and mortality infections in hospitals worldwide is methicillin-resistant Staphylococcus aureus. Therefore, there is a need to develop new antibacterial agents to treat these infections, and natural products are a rich source of them. In previous studies, we reported that lignan 3′-demethoxy-6-Odemethylisoguaiacin, isolated and characterized from Larrea tridentate, showed the best activity towards methicillin-resistant S. aureus. Thus, the aim of this study was to determine the potential molecular mechanism of the antibacterial activity of 3′-demethoxy-6-Odemethylisoguaiacin against methicillin-resistant S. aureus using microarray technology. Results of microarray genome expression were validated by real-time polymerase chain reaction (RT-PCR). The genetic profile expression results showed that lignan 3′-demethoxy-6-O-demethylisoguaiacin had activity on cell membrane affecting proteins of the ATP-binding cassette (ABC) transport system causing bacteria death. This molecular mechanism is not OPEN ACCESSMolecules 2015, 20 12451 present in any antibacterial commercial drug and could be a new target for the development of novel antibacterial agents.