Keywords
Pasak Bumi, Eurycoma longifolia, Trivalvaria macrophylla, Rennelia elliptica, antimicrobial activity
This article is included in the ICTROPS 2018 collection.
Pasak Bumi, Eurycoma longifolia, Trivalvaria macrophylla, Rennelia elliptica, antimicrobial activity
Pasak Bumi is a plant used in traditional medicinal that grows in the tropical forests of Kalimantan of Indonesia. It is used by the local people as an aphrodisiac, for postpartum treatment, fever, and malaria1,2. In Central Kalimantan, there are three different plant species on Pasak Bumi; Yellow Pasak Bumi (Eurycoma longifolia Jack., Simaroubaceae), Red Pasak Bumi (Rennelia elliptica, Rubiaceae) and Black Pasak Bumi (Trivalvaria macrophylla, Rubiaceae)3. Previous research of Pasak Bumi (E. longifolia Jack) from different regions has shown activity in inhibiting the growth of microbes, however, research on the other species of Pasak Bumi such as Rennelia elliptica and Trivalvaria macrophylla are still limited. From the above information, the research aim is to compare the inhibition activities of the three different plants against one yeast: Candida albicans, and three bacterias: Staphylococcus aureus, Streptococcus mutans, and Streptococcus sobrinus. The research was also designed to extend our knowledge and help us explore the antimicrobial activities of the three different plant species.
One kilogram of each plant was excavated and harvested from Katingan district, Central Kalimantan. The root was chopped and separated from its stem and leaves. The roots were sliced into small sections with a knife and allowed to dry under shade. The dried samples were crushed into powder using an electric blender. Once crushed, 50 grams of each powder of the plant root was weighed using a digital balance (Mettler Toledo, Mettler-Tokyo Group). Furthermore, the powder was extracted using successive maceration with the following solvents: n-hexane, ethyl acetate, and 96% ethanol. The ethanol filtrate was evaporated under a vacuum rotary evaporator (Eyela, N-N series) at 35°C until dry and used for the present study (Figure 1).
The total phenolic content was determined spectrophotometrically (UV Mini 1240 Shimadzu) in accordance to the Folin-Ciocalteu method4. The sample solution was prepared by dissolving the dry extracts (2 mg) in 100 μl DMSO and 900 μl of distilled water. The reaction mixture was made by mixing 200 µl of the extract from sample solution (200 μg/mL), 300 μl of distilled water, 250 μl of 10% Folin-Ciocalteu reagent (Merck Millipore, CAS No. 109001) and 1250 μl of 7.5% sodium carbonate. After a 90 minutes incubation at room temperature, the absorbance was determined spectrophotometrically at 760 nm. Gallic acid (Wako, CAS No. 5995-86-8) was used as a reference standard for plotting a calibration curve (concentration range: 2 to 10 μg/mL). The total phenolic content was expressed as a Gallic Acid Equivalent (GAE)/mg extract, using a standard calibration graph.
Four pathogenic microbial strains; C. albicans (CA), S. aureus (SA), S. mutans (SM) and S. sobrinus (SS) from the Forest Product Chemistry Laboratory’s culture collections, were used for the present study. The in vitro activity was screened using the agar well diffusion method in Nutrient Agar medium5,6. The extracts of each plant at a concentration of 10 mg/ml in 40% ethanol were prepared, and an aliquot of the test solution was put in to get a final concentration of 100, 250, 500, and 1000 μg/well. It was then placed on the inoculated nutrient agar plates and incubated for ±18–24 h at 37˚C. Ten μg/well of chloramphenicol (PT. Indofarma, Tbk., Indonesia) and 40% ethanol were employed as a positive and negative control. After incubation, the diameter of the inhibition zones was measured by a ruler. The experiment was performed in triplicate. The antimicrobial index (AI) was calculated using the formula6,7: Activity index (AI) = Inhibition Zone of the sample/Inhibition Zone of chloramphenicol.
All experiments were conducted three times. Regression analysis was used to make a calibration curve and calculate the total phenol content. All statistical analyses used Microsoft Excel 2010 software.
The total phenolic contents were calculated using the following linear equation based on the calibration curve of gallic acid: y = 0.0667x + 0.009; R2 = 0.9948, where y is absorbance and x is amount of gallic acid in µg (Table 1). T. macrophylla root extract obtaining higher total phenolic content in comparison to E. longifolia and R. elliptica. The extracts exhibited dose-dependent antimicrobial activities (Figure 2), and the results indicated that the in vitro antimicrobial activity of the T. macrophylla, E. longifolia, and R. elliptica extracts were ranked in the following order; SS>SM>SA>CA; SA>SM>SS>CA; and SS>SA>CA>SM, respectively. The highest activity was found in E. longifolia against S. aureus, with a maximum AI value (0.96) at 1000 μg/well concentration while the lowest activity at all concentration was found in R. elliptica extracts.
Plant extracts with a high AI value indicates that the extracts have good antimicrobial activity against the selected pathogens6. The inhibitory activity of E. longifolia root extracts was in agreement with previous literature, it could inhibit S. aureus8–10 and C. albicans11. R. elliptica was found to be able to inhibit the growth of C. albicans and S. aureus, which is contrary to a previous study where it was found to be inactive12; however, there was no information about the extraction method for R. elliptica and the concentration used on that study. So far there have been no reports of the T. macrophylla being antimicrobial, but in this study T. macrophylla has proven to be an inhibitor for the growth of S. aureus, S. mutans, S. sobrinus and C. albicans. This is believed to be the first report to explore and compare the antimicrobial potentials of the three different Pasak Bumi plants. The antimicrobial activity may be attributed to the high content of the phenols present. Phenolic compound such as gallic acid can causes irreversible changes (such as charge, intra and extracellular permeability, and physicochemical properties) in the properties of microbial membranes, with consequent leakage of essential intracellular constituents13. E. longifolia possess a higher antimicrobial activity than T. macrophylla, but its phenolic content was lower than T. macrophylla. E. longifolia extract might contain more non-phenolic compounds, or possess phenolic compounds that contain a higher number of active groups than the other extract. The interactions between chemical compounds (phenolic and non-phenolic compounds) might also be responsible for the antimicrobial effects14.
The present study performed in vitro studies of antimicrobial properties of three different Pasak Bumi (E. longifolia Jack, R. elliptica and T. macrophylla) on oral pathogens which gave positive results and different degree of activity.
Underlying data is available form Open Science Framework
OSF: Dataset 1. Pasak Bumi root extract, https://doi.org/10.17605/OSF.IO/Q6X7R15
License: CC0 1.0 Universal
This work was supported by the Forest Product Chemistry Laboratory, Forestry Faculty of Mulawarman University 2017/2018 and DIPA B2P2EHD 2017.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
The authors gratefully acknowledge the Dipterocarps Forest Ecosystem Research and Development Center, Samarinda, East Kalimantan and members of the Laboratory of Forest Products Chemistry, Mulawarman University.
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Is the work clearly and accurately presented and does it cite the current literature?
Partly
Is the study design appropriate and is the work technically sound?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Microbial Infections, Natural Products
Is the work clearly and accurately presented and does it cite the current literature?
Yes
Is the study design appropriate and is the work technically sound?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
Yes
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
References
1. Mohd Effendy N, Mohamed N, Muhammad N, Naina Mohamad I, et al.: Eurycoma longifolia: Medicinal Plant in the Prevention and Treatment of Male Osteoporosis due to Androgen Deficiency.Evid Based Complement Alternat Med. 2012; 2012: 125761 PubMed Abstract | Publisher Full TextCompeting Interests: No competing interests were disclosed.
Reviewer Expertise: process engineering, essential oil, microbiology
Alongside their report, reviewers assign a status to the article:
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