PHYTOCHEMISTRY AND ANTIMICROBIAL PROPERTIES OF SECONDARY METABOLITES FROM SEEDS OF ALPINIA (ZINGIBERACEAE)

• Main Author: JUWITANINGSIH, TITA
• Format: Dissertations
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/24542
• Institution: Institut Teknologi Bandung

Searching for new antibiotics have attracted many researchers due to many cases of bacterial resistance against existing antibiotics. One of the sources to find these compounds are from plants, including the plants of Alpinia (Zingiberaceae), which are locally known as “Lengkuas”. This genus has been used as traditional medicines, and a number of studies have also showed that extracts of several species of Alpinia were potential as antimicrobials. Phytochemical studies have shown that Alpinia produced secondary metabolites of terpenoid and aromatic derivatives, however studies related to their biological properties as antimicrobes were still very limited. Objectives of the research are to isolate secondary metabolites from the seeds of A. malaccensis and A. regia, and to determine their antimicrobial properties against pathogenic bateria and fungi. Secondary metabolite’s isolation was carried out including extraction, fractionation, and purification steps using a number of chromatographic techniques. Molecular structures of the isolated compounds were determined based on the analysis of NMR (1D and 2D) and mass spectral data. Assays for antimicrobial activities were conducted using standards of CLSI M07- A9 (antibacterial) and CLSI M38-A2 (antifungal) against seven pathogenic bacteria of ATCC strains, eight clinical isolates bacteria, and three species of Candida. Antimicrobial activities were expressed by MIC and MBC values. Compounds with significant activities were subjected to time-kill studies.Seven compounds have been succesfully isolated, four obtained from the seeds of A. malaccensis, namely 5,6-dehydrokawain (1), malacavalactone (2). (4E,6E)- <br /> <br /> <br /> <br /> 1,7-diphenylhepta-4,6-dien-3-one (3) and (5R)-trans- 1,7-diphenyl-5-hydroxyhept-6-en-3-one (4), and three compounds from the seeds of A. regia, namely galanal A (5), galanal B (6) and myogadial (7). Compound 2 was a new kavalactone derivative, while the rest were known metabolites, either they have been isolated from other species of Alpinia or from other genera in the family Zingiberaceae. Thus, the presence of compounds 1 – 7 in the two Alpnia species have significances to the chemotaxonomy of Alpnia, as well as their relationship within Zingiberaceae.On biological evaluations, the acetone extracts of both seeds exhibited moderate to weak antimicrobial properties (MIC values were in the range of 156 – 5000 ?g/mL). The pure malakavalactone (2) showed a relatively high anti-Candida activities (MIC 30 µM), while the other compounds (3 – 7) had variable antimicrobial activities ranging from high to weak levels (MIC 19 - >2183 µM). High antimicrobial activities were showed by (4E,6E)-1,7-diphenylhepta-4,6- dien-3-one (3), (5R)-trans-1,7-diphenyl-5-hydroxyhept-6-en-3-one (4) and miogadial (7). Refering to the antibacterial activities, the seven compounds were more active to the Gram-negative than to the Gram-positive bacteria. Not only as antibacterial, the seven compounds were also active as antifungi to Candida sp. Based on the results of time-kill assays, compound 2 could kill C. albican ATCC <br /> <br /> <br /> <br /> 10231 within 2 hours at a concentration of 2x MICs (= 60 µM), while compound <br /> <br /> <br /> <br /> 3 was able to kill K. pneumoniae ATCC 13 773 within 0.5 hours at a concentration of 4x MICs (= 190 µM) and against B. cereus ATCC 21772 within <br /> <br /> <br /> <br /> 1 hour at a concentration of 4x MICs (= 190 µM). The same effect was shown by compound 4 against K. pneumoniae which can kill in 0.5 hours at a concentration of 4x MICs (= 178 µM), and compound 7 was able to kill B. cereus ATCC 21772 in 0.5 hours at a concentration of 4x MICs (= 78 µM). The study of structure-activities relationship showed that the presence of a farnesyl at compound 2 could enhance very significantly its antimicrobial properties compared to the parent compound 1. In the diarylheptane group, the presence of hydroxyl group at C-5 of the heptane chain (compound 4) and a double bond at C-4 of the heptane chain (compound 3) gave a positive effect to the antibacterial activities. In the labdane group, a high antimicrobacterial activities of compound 7 could be due to the presence of a 1,4-dialdehyde group in which one of them is conjugated with a double bond. In addition, the different stereochemistry of the hydroxyl group in galanal A (5) and B (6) had a role to the differences of their antimicrobial properties. In conclusion, this research has successfully isolated a new compound malakavalactone (2) along with six known compounds. The seven compounds have been evaluated for their potencies as antimicrobials resulting that several compounds were potential to be developed as new antimicrobial agents. <br />