Sifat Anti mikrobial dari Metabolit Sekunder tanaman Nur Hidayat

Pendahuluan Berbagai organisme hidup dan tumbuh di dunia Ada interaksi antar organisme tersebut sehingga terjadi hubungan yang saling menguntungkan ataupun merugikan Interaksi tersebut dapat menghasilkan senyawa baru dan umumnya merupakan metabolit sekunder

Interaksi tanaman dan mikroorganisme Tanaman dapat berinteraksi dengan berbagai mikroorganisme dan berbagai bentuk interaksi Salah satu bentuk interaksi adalah parastisme yaitu penyerangan bakteri atau jamur pada tanaman yanng dapat menyebabkan penyakit pada tanaman (plant – pahogen interaction) Jika cocok maka mikroorganisme akan dapat tumbuh dan menyebabkan tanaman sakit jika tidak maka mikro tsb akan mati atau tidak tumbuh. Dasar ketahanan tanaman dari patogen ada dua – specific plant disease resistance – non-specific plant disease resistance

Specific plant disease resistance (host resistance) Resistensi spesifik terjadia karena adanya kesesuaian gen – gen dari tanaman dan penyebab penyakit. Tanaman meletakkan beberapa senyawa shg menghambat pertumbuhan mikroorganisme Sbg contoh tanaman lobak menghasilkan 1,3- β-glucanase, yang dapat melindungi dari serangan jamur Phytophthora infestans dan

Non-specific plant disease resistance (non-host resistance) Mikroorganisme menyerang tanaman dan tidak spesifik. Pertahanan tanaman menjadi tidak spesifik Ada dua strategi yang diterapkan: – constitutive defence mechanism

The constitutive defence mechanism Menghasilkan senyawa yg berfungsi melawan bakteri, jamur dan virus dengan menghasilkan senyawa-senyawa bererat molekul rendah: cyanogenic glycosides, mustard oil, glycosides, alkaloids, phenols, essential oils dan tannin. Menggunakan perlindungan fisik seperti bentuk rambut, paku, duri, kulit keras dan sebagainya

infection-induced defence mechanism Tanaman menghasilkan senyawa, apabila ada serangan mikroorganisme Pada keadaan normal senyawa ini tidak dihasilkan.

Rapid plant defence response 1. Changes in plasma membrane ion flux (e.g. Ca2+, K+, H+). 2. Generation of active oxygen species (oxidative burst). 3. Protein phosphorylation cascades. 4. Production of hydroxyproline-rich glycoproteins to strengthen the cell wall barrier to pathogens. 5. Initiation of phytoalexin synthesis. 6. NO (nitric oxide) accumulation. NO has a key role in plant pathogen response. 7. Hypersensitive response. Hypersensitive cell death is a mechanism widely used by hosts to prevent the spread of pathogens, and in some cases, killing them.

Phytoalexins Mikroorganisme yang menyerang tanaman dapat ditolak tanaman oleh reaksi hipersensitif tanaman. Apabila sel tanaman diserang jamur, maka sel- sel tanaman disebelahnya akan mati berwarna coklat (nekrosis)shg jamur tidak tumbuh menyebar. Pada nekrosis sering ditemukan senyawa antibiotik yg disebut phytoalexin.

Chemical structures and distribution Phytoalexins (Greek: phyton, meaning plant; alexis, meaning defence) are defined as low- molecular-weight and antibiotically effective substances of plant secondary metabolism, the synthesis and accumulation of which is induced by pathogens or herbivores (M¨ uller and Borger, 1940).

The induction of phytoalexin synthesis in plant tissue has been studied mainly in pathogenic fungi; however, studies of attacks by viruses, bacteria, nematodes, arachnida and insects have also been conducted. Correspondingly, antibacterial, fungistatic and nematostatic phytoalexins have been discovered, as have those which deter insects from feeding.

These substances usually demonstrate a biostatic or biocidal effect at relatively low concentrations ( to M/L). At present, we are aware of over 350 different phytoalexins in more than 100 plant species. Their molecular structures reflect the variation in secondary plant metabolic pathways, since phytoalexins can be found among the alkaloids, coumarins, dihydrophenanthrenes, flavonoids, isoflavonoids, phenols, polyacetylenes, steroids, stilbenes and terpenes

Specificity of phytoalexin accumulation 1. ‘Localization and timing of phytoalexin accumulation in infected tissue in relation to pathogen development.’ 2. ‘Phytoalexins must accumulate to antimicrobial levels at the infection site in resistance plants in sufficient concentrations to inhibit the pathogen at the time pathogen development is stopped.’

Specificity of phytoalexin accumulation 3. ‘Strong positive correlation of rapid phytoalexin production with incompatible interactions in gene-for-gene plant pathogen systems.’ 4. ‘Association of rapid phytoalexin accumulation with resistance genes that condition restriction of pathogen development.’ 5. ‘Use of metabolic inhibitors that enhance susceptibility and block phytoalexin production.’

Specificity of phytoalexin accumulation 6. ‘A positive relationship between pathogen virulence and tolerance of phytoalexins.’ 7. ‘An increase of plant tissue resistance by stimulation of phytoalexin production prior to inoculation.’ 8. ‘There must be evidence that the phytoalexins are directly involved in defence, and that this defence role has a measurable benefit for the plant.’

Specificity of phytoalexin accumulation In general, the levels of phytoalexin in the plant tissue are regulated by new synthesis and degradation of secondary metabolites. Phytoalexins are synthesized relative quickly after contact with the attacking pathogen. After a lag phase, at a minimum of 2 h, the bioactive substance can be measured and the amounts increase during the following hours and days for up to about 96 h, sometimes longer, until maximum accumulation has been achieved. Subsequently, the levels of phytoalexin decrease to those which existed before the attack. This means that high levels of phytoalexin accumulation do not persist in plants once a pathogen or stress has been contained and plant metabolism has returned to normal

Essential oils with antimicrobial activity (1)gram-positive bacteria, e.g. Bacillus cereus, Bacillus subtilis, Mycobacterium intracellulare, Sarcinia flava, Sarcinia lutea, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, Streptococcus hemolyticus and Streptococcus pneumoniae; (2)gram-negative bacteria, e.g. Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Klebsiella pneumoniae, Proteus mirabilis, Proteus morgani, Proteus rettgeri, Pseudomonas aeruginosa. Salmonella enteritidis, Salmonella typhosa, Salmonella typhimurium, Shigella flexneri and Shigella sonnei; (3)yeasts, e.g. Candida albicans, Candida kruzei, Candida tropicalis, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Torula glabrata, Torulopsis utilis, Torulopsis glabrata and Trichosporon capitatum; and (4)fungi, e.g. Aspergillus fumigatus, Aspergillus niger, Aspergillus ochraceus, Epidermophyton flocosum, Fusarium sporotrichoides, Fusarium tricintum, Microsporum canis, Penicillium rubrum, Penicillium spinulosum, Trichophyton rubrum and Trichophyton mentagrophytes.

Isolated secondary plant metabolites with antimicrobial properties Alkaloid Aliphatic aldehydes Anthraquinones Diterpenoids Monoterpenoids Flavonoids

Alkaloid Bioactive alkaloids could be found within acridone-, aporphine-, benzophenanthridine-, bisbenzylisoquinoline-, indole-, isoquinoline-, piperidine-, protoberberine-, quinoline-, terpenoid- and steroid-type alkaloids Dictamnine, a furoquinoline alkaloid, isolated from the root bark of Dictamnus dasycarpus (a traditional Chinese medicine), exhibited strong antifungal activity against the pathogenic fungus, Cladosporium cucumerium (minimal concentration required to cause 50% inhibition [MIC μg/mL]).

Aliphatic aldehydes Olive oil derived from Olea europaea (Oleaceae) has been used worldwide in traditional medicine to treat skin diseases. Oleuropein and hydroxytyrosol, two secoiridoids contained in olive oil, are known for their antibacterial activities. It was hypothesized that these phytoagents act not only on the plasmatic membrane but also on intracellular targets

Anthraquinones and Diterpenoids Anthraquinonic compounds, traditionally used as laxatives, possess many other pharmacological properties, including microbiological action Diterpenoids lanigerol and forskalinone, isolated from the roots of Salvia lanigera and Salvia forskahlei, respectively, demonstrated moderate antibacterial activity against gram- positive bacteria