Keywords
Tampoi, Baccaurea macrocarpa, toxicity, BSLT, antioxidant, DPPH
This article is included in the ICTROPS 2018 collection.
Tampoi, Baccaurea macrocarpa, toxicity, BSLT, antioxidant, DPPH
Indonesia is a mega-diverse country in terms of biodiversity that is flanked by the Indian and Pacific Oceans. Indonesia's biodiversity encompasses the diversity of living things both on land and sea1. Indonesia, especially East Kalimantan, has very extensive tropical rainforest, which is a habitat for much biodiversity. Various types of plants have long been utilized by the community as traditional medicines. The utilization of natural products as an alternative medicine is increasing because natural ingredients are believed to be safer than synthetic substances, i.e. do not contain chemicals that only can be found in modern medicines, which are linked to toxicity2.
Among plants, the genus of Baccaurea have interesting biological activities. For example, B. angulata has been reported as a potential functional food with effective antioxidant3, anti-inflammatory, anti-atherogenic, and hypocholesteromia activities4. Other research has also investigated the biological activity of other species of this genus, i.e. B. lanceolata and B. macrocarpa. It was reported that the fruits of B. macrocarpa exhibited the highest antioxidant activity compared with B. lanceolata, which significantly correlated with the phenolic and flavonoid contents5.
B. macrocarpa is one of the typical plants of East Kalimantan, Indonesia and the edible fruits is a source of additional nutrients and known as Tampoi. Until now, the information about the antioxidant activity of other parts of this plant such as the bark of Tampoi has not been reported yet. Hence, the present research was conducted to investigate the phytochemical, toxicity, and antioxidant activity of the bark of Tampoi (B. macrocarpa). Furthermore, the gas chromatography-mass spectrometer (GC-MS) analysis was performed to obtain information about the kinds of isolated compounds contained.
Extraction was carried out as described previously by Erwin et al. (2014)6. The bark of Tampoi (B. macrocarpa) was dried for 1 week at room temperature and ground to a powder. The powder was extracted using a maceration method by soaking in methanol for 24 hours at room temperature, which was repeated three times. Afterwards, the extract solution was filtered by filter paper and the solvent was evaporated under vacuum using a rotary evaporator (Buchi R II) at 45°C and 1 atm, to obtain the methanol extract of bark of Tampoi.
Phytochemical evaluation was performed to investigate the secondary metabolites contents of the methanol extract of bark of Tampoi (B. macrocarpa), including alkaloids, flavonoids, phenolics, steroids, triterpenoids, and saponins, as described previously7. The presence of secondary metabolites were identified by observing the changing color of the extract. These evaluations were performed as follows:
Alkaloids. 1 mg of extract was inserted into a test tube and then diluted in 1 mL methanol. Then a few drops of H2SO4 1M was added. Afterwards, a few drops of Dragendorff reagent was added into the mixture. The formation of orange on filter paper indicated the presence of alkaloids.
Flavonoids. 1 mg of extract was inserted into a test tube and diluted in 1 mL methanol. A few 2 mg of Magnesium powder was added followed by a few drops of concentrated HCl. The presence of flavonoids was identified by the formation of pink or red color.
Phenolics. 1 mg of extract was introduced into a test tube and dissolved in methanol. Then a few drops of 1% FeCl3 were inserted. The formation of green, red, purple, dark blue or black indicated the presence of phenolics.
Steroids and triterpenoids. 1 mL of methanol and 1 mg of extract were inserted into a test tube, stirred until homogeneous, then 2 drops of anhydride acetate and 1 drop of H2SO4 were added (Liebermann Burchard reagent). The formation of green or purple precipitation showed a sample containing steroids, and red precipitation displayed the presence of terpenoids.
Saponins. 1 mg extract was put into a test tube and then dissolved in distilled water, and shaken strongly. The presence of saponins is characterized by the formation of durable foam on the surface of the liquid. Foam that remains stable after the addition of a few drops of concentrated HCl indicated the presence of saponins.
The toxicity test of extract was performed using brine shrimp lethality test (BSLT), as described previously8. Methanol extract of bark of Tampoi (B. macrocarpa) (1 mg) was dissolved using 100 µL of 1% DMSO (dimethyl sulfoxide) and homogenized. The samples were diluted using 150 µL of distilled water until the total of volume reached 250 µL, and then pipetted 200 µL and diluted again using 600 µL of distilled water until the total of volume was 800 µL, so that the sample concentration was 1000 ppm. Samples with a concentration of 500, 250, 125, 62.5, 31.2, 15.6, and 7.8 ppm were made from sample dilutions of a concentration of 1000 ppm. The control solution was made with the same treatment as the sample without the addition of extract.
The toxicity test was carried out using several standard micro plates. About 100 µL seawater containing 8-13 shrimp larvae was added to each diluted sample so that the sample volume was 200 µL (with a concentration of 500, 250, 125, 62.5, 31.2, 15.6, and 7.8 ppm). The number of dead shrimp larvae was calculated for 24 hours after treatment. Each sample was treated in triplicate. The data obtained was recorded and the value of LC50 calculated (Lethal Concentration 50%) using SAS Probit analysis.
The antioxidant activity of the extract was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging method, as described previously7,9–11. Briefly, the extract of bark of Tampoi (B. macrocarpa) was prepared in a solution with a concentration of 25, 50, 75 and 100 ppm, respectively. 1 mL of extract and 1 mL of DPPH (0.024 mg/mL) were put into a test tube, which was incubated for 30 min at 37°C before being measured by Spectrophotometer UV Thermo Scientific Evolution 201 (measurements were carried out at a wavelength of 515 nm). Vitamin C was used as a positive control with variations in concentration were 2, 4, 6, and 8 ppm, respectively. Determination of antioxidant activity or DPPH scavenging effect (%) of extract and vitamin C were carried out in triplicate using equation as follow.
Then, the value of IC50 (Inhibitory Concentration 50%) was determined using linear regression.
In order to obtain the information of the kinds of compounds in methanol extract of bark of Tampoi, an analysis using GC-MS 5977 was performed. Specification of column that used in this research was HP-5MS with length 30 m, diameter 0.25 mm, thick of film 0.25 µm. The identification of the compound was compared to NIST standard data (https://webbook.nist.gov).
The secondary metabolites found in the methanol extract of the bark of Tampoi (B. macrocarpa) are presented in Table 1.
Secondary metabolites | Bark |
---|---|
Alkaloids | + |
Steroids | + |
Triterpenoids | + |
Flavonoids | + |
Phenolics | + |
Saponins | ˗ |
To evaluate the antioxidant activity of the methanol extract of the bark, DPPH method was performed. The results of the antioxidant test can be seen in Table 2.
Average of three replicates performed for each concentration.
Furthermore, the methanol extract was analyzed using GC-MS analysis. The chromatogram and it compound contents of this extract is shown in Figure 1 and Table 3, respectively.
Based on the phytochemical evaluation, the results showed that the methanol extract of bark of Tampoi (B. macrocarpa) contains several secondary metabolites including alkaloids, flavonoids, phenolics, steroids, and triterpenoids. Several secondary metabolites including alkaloids, steroids, triterpenoids, flavonoids, and phenolics are known to have antioxidant properties. These antioxidant compounds wield their activities through different mechanisms, for example by inhibiting hydrogen abstraction, radical scavenging, binding transition metal ions, disintegrating peroxides12,13, and one of the most important factors influencing antioxidant activity is the ability of the compounds to donate electrons.
Furthermore, in the present study the antioxidant activity of the Tampoi extract was determined by DPPH method. This method was used because it is simple, efficient, quick, more practical, and relatively inexpensive14. Based on Table 2, it is known that the methanol extract of bark of Tampoi (B. macrocarpa) can be categorized as an active extract in an antioxidant assay with IC50 value of 11.15 ppm. In addition, the results of the toxicity test using the BSLT method showed that the extract was toxic because it displayed LC50 value above 1000 ppm.
According to the results of GC-MS analysis, the chromatogram showed 37 peaks (compounds). The profile of the compounds showed that the main components were fatty acids and fatty acid esters. Total content of unsaturated fatty acids and esters with a peak area of 12.15% including 9,12-octadecadienoic acid (Z,Z)-, methyl ester (peak area 0.04), 9-octadecenoic acid, methyl ester (peak area 8.46), undec-10-ynoic acid, undecyl ester (peak area 3.58), undec-10-ynoic acid, undecyl ester (peak area 3.346), cis-vaccenic acid (peak area 0.07), and oleic acid (peak area 0.19). It was been reported that unsaturated fatty acid compounds and unsaturated fatty acid esters have significant antioxidant properties15–17.
It can be seen that only a small part of those are aromatic compounds. However, aromatic compounds are compounds that have the ability to stabilize high free radicals. The mechanism of phenolics as antioxidants is started by the formation a bond between free radical (DPPH radical) and hydrogen atom from OH-phenolics (ArOH) to form ArO. radical. Hydrogen atom will easier to be released because of the presence of electron withdrawing group which is bound at ortho- or para- positions18. Furthermore, ArO will react with a radical (ArO. or other radical) to form a stable compound19,20.
DPPH. + AOH → DPPH-H + ArO.
DPPH. + ArO. → DPPH-OAr or DPPH. + R. → DPPH-R
According to identification of the compound in the methanol extract of bark of Tampoi (B. macrocarpa) using NIST database (DRUGBANK accession number, DB14212), it is known that the compound is identified as methylparaben. Based on the NIST database, peak at retention time at 9.467 min and peak area of 0.76% showed the characteristic of methylparaben (Molecular formula=C8H8O3; Molecular weight=152).
It has been reported that methylparaben does not show negative effects on male mouse reproduction21. Methylparaben is widely used as a preservative in cosmetic products, medicines or pharmaceutical products and food ingredients22,23, and the antibacterial activity of methylparaben is stronger than benzoate acid24.
Methylparaben is a phenolic group that can reduce free radicals because it contains aromatic groups, -OH clusters and carbonyl groups. The presence of –COOCH3 substituent at para- position in methylparaben makes this compound act as an electron withdrawing group. The bond dissociation energy (BDE) of the O–H bond is a main factor to investigate the action of antioxidant, due to the weaker OH bond the reaction of the free radical will be easier19. As the prediction of the previous reaction mechanism7,19, the prediction of the reaction mechanism between DPPH radical and methyl paraben can be seen in Figure 2.
The results of the study showed that the bark of Tampoi (Baccaurea macrocarpa) has antioxidant activity with an IC50 value of 11.15 ppm.
F1000Research: Dataset 1. Sheet 1, raw data of the results of phytochemical evaluation for alkaloids, flavonoids, phenolics, steroids, triterpenoids, and saponins by observing the changing of colors; Sheet 2, raw data of the observation of the mortality numbers of Artemia salina Leach and calculation of LC50 value in toxicity test using brine shrimp lethality test; Sheet 3, raw data for antioxidant activity by DPPH method, including the measurement of absorbance using spectrophotometer in triplicate, the calculation of percentage of antioxidant activity, and the value of IC50; Sheet 4, raw data of GC-MS analysis., https://doi.org/10.5256/f1000research.16643.d22722225
The authors acknowledge funding from the Islamic Development Bank (IsDB) project in the frame of Hibah Penelitian PIU IDB for Lecturer Mulawarman University 2018 Number: 2248/UN17.11/PL/2018.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
The authors would like to thank the IsDB project for providing financial support and Head of Plant Anatomy and Systematic Laboratory of Biology Department, Faculty of Mathematics and Natural Sciences of Mulawarman University for identification the specimen.
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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?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
Not applicable
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: Natural Product Chemistry.
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?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
Not applicable
Are all the source data underlying the results available to ensure full reproducibility?
Partly
Are the conclusions drawn adequately supported by the results?
Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Natural Product Chemistry and Organic Synthesis
Is the work clearly and accurately presented and does it cite the current literature?
No
Is the study design appropriate and is the work technically sound?
No
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
I cannot comment. A qualified statistician is required.
Are all the source data underlying the results available to ensure full reproducibility?
No
Are the conclusions drawn adequately supported by the results?
No
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Pharmacology, Biomedical sciences
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?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Not applicable
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: Plant Phyto chemistry
Alongside their report, reviewers assign a status to the article:
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