Comparative study of different Malaysian Stingless bee propolis: Physicochemical characterization, Phytochemical contents and Antibacterial activity

 

 

Rozaini Mohd Zohdi1,2*, Nurul Najihah Yaacob3, Nur Azyan Mohd Hasif3,

Muhammad Amirul Adli1,2, Monporn Payaban4, Richard Johari James1,5, Fahimee Jaapar6

1Atta-ur-Rahman Institute for Natural Product Discovery, Universiti Teknologi MARA Selangor Branch,

Puncak Alam Campus, 42300 Puncak Alam, Selangor, Malaysia.

2Faculty of Pharmacy, Universiti Teknologi MARA, Selangor Branch, Puncak Alam Campus, 42300

Puncak Alam, Selangor, Malaysia.

3Faculty of Applied Sciences, Universiti Teknologi MARA, Selangor Branch, 40450 Shah Alam,

Selangor, Malaysia.

4Faculty of Science, Rangsit University, Muang-Ake, Paholyothin Rd., PathumThani 12000, Thailand.

5Integrative Pharmacogenomics Institute (iPromise), Universiti Teknologi MARA Selangor Branch,

Puncak Alam Campus, 42300 Puncak Alam, Selangor, Malaysia.

6Agrobiodiversity and Environmental Research Centre, MARDI Headquarter, 43400, Serdang,

Selangor, Malaysia.

*Corresponding Author E-mail: rozainizohdi@uitm.edu.my

 

ABSTRACT:

Stingless bee propolis is known to contain a variety of bioactive compounds, including phenolic and flavonoids, which have been linked to its antibacterial properties. Nevertheless, the phytochemical compositions of stingless bee propolis are significantly influenced by a complex interplay of multiple factors such as geographical origin, floral source, and bee species. This study aimed to assess the physicochemical properties, phytochemical contents, and antibacterial activity of propolis from different stingless bee species found in the same environment and ecological system. The propolis samples obtained from Heterotrigona itama, Geniotrigona thoracica and Tetrigona apicalis were subjected to physicochemical analysis to determine the pH, moisture, lipid, resin, and wax contents. The total phenolic content (TPC) and total flavonoid content (TFC) were measured by Folin-Ciocalteu colorimetric and aluminium chloride methods, respectively. The antibacterial activity was determined using the agar well diffusion method against four Gram-positive bacteria, including Bacillus cereus, Micrococcus luteus, Streptococcus mutans, and Staphylococcus aureus. The physicochemical analysis of the propolis samples yielded the following results: moisture (12.17-16.45%), lipid (2.95-9.48%), resin (39.00-51.00%), wax (26.50-37.00%), and pH (5.07-5.61). Results revealed that propolis produced by G. thoracica displayed significantly higher moisture (16.45±0.38%), and resin contents (51.00±1.41%), as well as significantly lower percentage of lipid (2.95±0.12%), and wax content (26.50±0.71%). Similarly, G. thoracica propolis extract exhibited significantly higher TPC (200.70±0.06mg/mL GAE) and TFC (141.60±3.63mg/mL QE) values compared to the other propolis samples. Additionally, G. thoracica propolis extract was significantly active against B. cereus and M. luteus with inhibition zones of 15.00 and 16.00, respectively, and minimum inhibition concentration (MIC) of 390.63μg/mL. A strong correlation was found between resin content, TPC and antibacterial activity of propolis. This study indicated that the presence of high resin content in propolis resulted in a high concentration of phenolic compounds, which contributed significantly to its antibacterial activities. Furthermore, the research highlighted the species-dependent effect of propolis on its physicochemical characteristics, phytochemical composition, and antibacterial properties. The observed antibacterial efficacy of G. thoracica propolis suggested that the propolis extract held promise as an alternative treatment option against bacterial infections. Further research is warranted to fully elucidate the specific phenolic compounds that could contribute to its antibacterial properties.

 

KEYWORDS: Stingless bee propolis, physicochemical, total phenolic content, total flavonoid content, well diffusion.

 


 

INTRODUCTION: 

Stingless bees, of the tribe Meliponini, are a diverse tribe of eusocial bees that are widely distributed in tropical and subtropical regions of the globe1. There are over 500 species of stingless bees worldwide, with the highest diversity found in the Neotropical region2. Stingless bees, known locally as ‘lebah kelulut’ in Malaysia, are efficient pollinators of both wild flowering and cultivated plants, playing a vital role in biodiversity conservation and food security3. With around 50 documented species of stingless bees in Malaysia, stingless beekeeping, also known as meliponiculture, has been experiencing a surge in interest owing to its profound ecological and economic importance3. In particular, H. itama, G. thoracica, and T. apicalis are among the frequently domesticated species in Malaysian meliponiculture industry4. G. thoracica is the largest stingless bee species endemic to Malaysia, measuring between 8.12-8.65 mm in body size5. Conversely, both H. itama and T. apicalis are relatively smaller species, with body sizes ranging from 5.5 to 6 mm and 3 to 7.5 mm, respectively6,7. Although all three species have black-coloured bodies, H. itama can be distinguished by its body size and monochromatic black colour pattern, whilst G. thoracica and T. apicalis have split-coloured wings with black at the base and white or clear colour on the apex region5.

 

Propolis is one of the stingless bee products, aside from honey and bee pollen. Stingless bees collect resins, nectar, and pollen from various plants to construct their hives and nourish themselves. Plant resins are mixed with cephalic glandular secretions to produce propolis and utilize it as a key component in their hives to protect against pathogens and other external threats8. For centuries, propolis has been utilized in traditional medicine due to its diverse therapeutic properties in treating a range of ailments such as allergies, cancer, oral health problem, lung, and skin infections9,10. Propolis has been reported to be an effective post-treatment disinfectant agent following root canal treatment to inhibit the growth of oral bacteria11,12. Moreover, propolis also shown to enhance osteoblast formation during orthodontic tooth movement13. The diverse range of biological activities and potential health benefits of propolis are attributed to its intricate blend of chemical compounds, which contribute significantly to the bioactive actions of propolis such as antibacterial, antifungal, antioxidant and antitumor activities8,14,15,16.

 

In general, propolis contains flavonoids, phenolic acids, terpenes, aromatic acids, and other compounds, such as vitamins, minerals, and trace elements17. The specific chemical compounds found in propolis can vary greatly depending on several factors, including geographical origin, botanical sources, and bee species18

 

The diverse foraging behaviour of stingless bees from a wide range of plants contributes to the complex chemical diversity of their propolis, leading to variations in its biological activity19,20,21. Moreover, the physicochemical properties and phytochemical compositions of propolis are important factors in determining its therapeutic potential20. While several studies have been conducted on the antibacterial activity of propolis, there is still a lack of comprehensive research focusing on the correlation between the physicochemical properties, phytochemical contents, and antibacterial activity of propolis among different stingless bee species. Hence, the aim of this study was to conduct a comparative analysis of the physicochemical properties, total phenolic and flavonoids contents, and antibacterial activity of propolis derived from three different stingless bee species inhabiting the same environment and ecological setting. In addition, the correlation between the physicochemical, phenolic, and flavonoid contents, and the antibacterial property was also evaluated. This research will provide valuable insights into the factors that contribute to the variations in propolis antibacterial activity among different bee species, aiding in its potential applications for various health-related purposes. 

 

MATERIALS AND METHODS:

Collection of raw propolis:

Propolis produced by stingless bees H. itama, G. thoracica, T. apicalis were collected in October 2022 from Ladang Mini Kelulut of Malaysian Agricultural Research and Development Institute (MARDI), Serdang, Selangor (N 3° 40’ 42.1818” E 10° 31’14.5416”) (Figure 1). The apiary site is predominantly surrounded by a diverse range of herbal plants, including Eurycoma longifolia, Labisa pumila, Clinacanthus nutans, Zingiber zerumbet, Andrographis paniculate and Orthosiphon stamineus. Additionally, ornamental plants, including Lagerstroemia langkawiensis, Livistona chinensis, Coleus amboinicus, and Samanea saman, as well as fruit trees such as Nephelium lappaceum, Mangifera indica, Garcinia mangostana, and Syzygium aqueum are also prevalent in the vicinity.  Voucher specimens of the three identified stingless bee species were deposited at MARDI museum with voucher accession numbers of H.I 2022 (H. itama), G.T 2022 (G. thoracica), and T.A 2022 (T. apicalis). Only propolis from the top of the colonies was collected for analysis purposes. The samples were cleaned under tap water, air-dried, and kept in labelled polyethylene bag at -20℃ prior to the analysis.

 

Figure 1: The images of stingless bee propolis of (A) H. itama, (B) G. thoracica, and (C) T. apicalis.

 

Preparation of propolis extract:

The ethanolic extract of propolis was prepared following the method described by Adli et al. (2022)21 with slight modification. Briefly, the propolis was macerated in ethanol and the suspension was agitated at 250 rpm for 48 h at the temperature of 25-28°C. The suspension was filtered, and the supernatant was rotary evaporated at 40°C. To eliminate the wax, the extract was kept overnight in a freezer at -18°C and centrifuged at 2500 rpm for 5 min. Subsequently, the supernatant was collected and freeze dried.

 

Physicochemical characterization of propolis samples:

The moisture content of different propolis samples was calculated according to the methods established by Association of Official Analytical Chemist (AOAC)22. The content of lipid, resin, wax, pH was estimated according to method described by Touzani et al. (2019)23. All the analyses were done in triplicates and the mean was determined.

 

Determination of Total Phenolic Content (TPC):

The determination of TPC in propolis extracts was performed using the Folin-Ciocalteu colorimetric method, following the protocol described by Pratami et al. (2018)24. The TPC values were expressed as milligrams per gram of Gallic Acid Equivalent (mg/g GAE). Gallic acid solutions with eight different concentrations ranging from 5 to 1000µg/mL were prepared. About 25µL of 1mg/mL extracts and standard solution were mixed with 100µL of Folin-Ciocalteu reagent in a 96-well microplate. The mixture was then incubated and shaken for four minutes at room temperature. Following this, 75µL of 7.5% sodium carbonate was added to the reaction mixture which was shaken for 60 seconds and further incubated for two hours at room temperature. The absorbency of the reaction mixture was measured at 765nm using a spectrophotometer (SPECTROstar Nano, BMG Labtech, Germany). The obtained absorbance values were plotted on a standard curve, generated from the regression line, to determine the TPC value. Each test was performed in triplicate.

 

Determination of Total Flavonoid Content (TFC)

The TFC of propolis extracts was measured using the aluminium chloride (AlCl3) colorimetric technique in accordance with the method described by Farasat et al. (2014)25. The TFC values were expressed as milligrams per gram of Quercetin Equivalent (mg/g QE).  To construct the quercetin standard calibration curve, various concentrations of quercetin (ranging from 10 to 500µg/mL) were prepared. About 20µL of the propolis extracts and the standard solution were mixed were added into a 96-well microplate. Subsequently, 20µL of 10% aluminium chloride solution, 20µL of 1M potassium acetate and 140µL distilled water were added to each well. The microplate was then vigorously shaken for 60 seconds and incubated in darkness for 30 minutes at room temperature. The absorbance of the reaction mixtures was measured at 415nm. The TFC values were calculated based on the linear regression line obtained from the quercetin standard calibration curve. All measurements were performed in triplicate.

 

Antibacterial activity:

a)    Bacterial strains and culture:

A total of four Gram-positive bacteria were used in this study, comprising of Bacillus cereus (ATCC 11778), Micrococcus luteus (ATCC 48732), Staphylococcus mutant (clinical isolate), and Staphylococcus aureus (ATCC 25923). All bacterial strains were maintained on nutrient agar slants at 4°C and subsequently cultured in Mueller-Hinton Broth (MHB) to obtain working bacterial cultures. The density of overnight bacterial culture was adjusted to 0.5 McFarland standards (1 x 108 CFU/mL) prior to antibacterial assay.

 

b)   Well diffusion assay:

The antibacterial activity of propolis extracts were determined by agar well diffusion method using Mueller-Hinton Agar (MHA) plates following Clinical and Laboratory Standards Institute (CLSI) guidelines26. The propolis extract of 50mg/mL concentration was prepared in 5% dimethyl sulfoxide (DMSO). The bacterial suspensions were inoculated on MHA plates using a sterile cotton swab. Wells with a 6 mm diameter were bored using sterile micropipette tips. Each well was filled with 100µL of propolis extract from different stingless bee species. Ciprofloxacin (5µg/mL) was used as positive control, while 5% DMSO served as negative control. The plates were incubated at 37°C for 24h. The antibacterial activity was determined by measuring the diameter of inhibition zones. The experiment was conducted in triplicates.

 

c)   Determination of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC):

To determine the MIC of the extracts against bacterial strains that showed sensitivity in the disc diffusion assay, a modified resazurin broth microdilution method was employed Sarker et al. (2007)27. First, a 96-well microtiter plate was prepared, and a 100mg/mL stock solution of each extract was diluted two-fold to concentrations ranging from 9000 to 25μg/mL. Next, a 50 μL bacterial suspension (1 x 106 CFU/mL) was added into each well using a micropipette. A set of controls was included in each microplate, including a sterility control with broth only, a growth control with broth and bacteria, and a negative control with 1% DMSO. Ciprofloxacin served as positive control. The plate was incubated at 37°C for 24hours, after which 10μL of 0.01% resazurin indicator solution was added to each well. The plate was incubated for an additional 2hours at 37°C under anaerobic conditions, and changes in colour were observed and recorded. The MIC was determined as the lowest concentration of extracts that exhibited a resazurin blue colour. Each experiment was conducted in triplicate.

 

After the broth microdilution assay, 10μL samples were taken from each well and sub-cultured onto MHA plates, which were then incubated at 37°C for 24hours. The minimum bactericidal concentration (MBC) was determined as the lowest concentration of extracts that did not show any bacterial growth.

 

Statistical analysis:

The data was presented as mean ± standard deviation (SD) and analyzed using GraphPad Prism version 7.0. One-way analysis of variance (ANOVA) followed by post hoc Tukey’s multiple comparison test was used for statistical comparisons. Pearson’s correlation coefficient was used to determine the relationship between resin, TPC, TFC and antibacterial. Differences were considered significant when P<0.05.

 

RESULTS:

Physicochemical characterization:

Table 1 shows the physicochemical characteristics of each propolis samples. In terms of moisture content, G. thoracica propolis showed significantly higher values at 16.45%±0.38 compared to H. itama and T. apicalis at 12.17%±0.47 and 3.44%±0.36, respectively. The lipid content ranged from 2.95 – 9.48%, with G. thoracica having significantly lower value compared to T. apicalis and H. itama. Additionally, G. thoracica exhibited significantly higher percentage of resin (51.00±1.41) and lower percentage of wax (26.50±0.71) compared to the other two propolis extracts. However, the pH of the propolis samples was in close range between 5.07-5.61.  

 

Table 1: Physicochemical characteristics of propolis samples from three different stingless bee species.

Propolis sample

Moisture (%)

Lipid (%)

Resin (%)

Wax (%)

pH

H. itama

12.17 ± 0.47a

8.15 ± 0.08b

40.09 ± 1.53a

37.00 ± 1.42b

5.07 ± 0.08a

G. thoracica

16.45 ± 0.38b

2.95 ± 0.12a

51.00 ± 1.41b

26.50 ± 0.71a

5.52± 0.05a

T. apicalis

13.44 ± 0.36a

9.48 ± 0.32b

39.00 ± 0.92a

36 .00 ± 1.41b

5.61 ± 0.03a

Note. Values in the same column with different letter is significant at p<0.05.

Total Phenolic and Flavonoid Contents:

As depicted in Table 2, the TPC and TFC of propolis extracts exhibited diverse values, ranging from 29.73 to 200.70mg/mL GAE and 9.33 to 141.6mg/mL QE, respectively. Notably, G. thoracica displayed significantly higher values for TPC (200.7mg/mL GAE) and TFC (141.6mg/mL QE) compared to the other two propolis extracts.

 

 

Table 2: Total phenolic and flavonoid contents of propolis samples determined by Follin-Ciocalteu and aluminium nitrate colorimetric methods, respectively.

Propolis sample

Total Phenolic Content (mg/mL GAE)

Total Flavonoid Content (mg/mL QE)

H. itama

134.03±4.09b

13.18±1.52a

G. thoracica

200.70±0.06c

141.60±3.63b

T. apicalis

29.73 ±1.63a

9.33±0.54a

Note. Values in the same column with different letter is significant at p<0.05.

 

 

 

Antibacterial activity:

The propolis extracts exhibited antibacterial activity against all tested Gram-positive bacteria, with inhibition zones ranging from 9.50 to 16.00mm (Table 3). G. thoracica propolis extract was significantly active against B. cereus and M. luteus when compared to H. itama and T. apicalis propolis extracts with inhibition zone of 17.00±0.00 and 15.00±0.00mm, respectively. Conversely, G. thoracica propolis extract did not exhibit significant difference in inhibiting S. mutans and S. aureus when compared to the other propolis extracts. Ciproflaxin, used as a positive control, demonstrated significant antibacterial activity against all tested bacteria, with inhibition zones ranging from 20.50 to 25.00mm.

 

 

 

Table 3: Zone of inhibition of ethanolic propolis extracts against selected Gram-positive bacteria.

Bacteria

Diameter of inhibition zones (mm)

H. itama

G. thoracica

T. apicalis

Ciproflaxin

B. cereus

9.67 ± 1.15a

15.00 ± 0.00b

9.50 ± 0.71a

21.00 ± 0.00c

M. luteus

12.50 ± 0.71a

16.00 ± 0.00b

13.00 ± 0.00a

25.00 ± 1.41c

S. mutans

10.50 ± 0.71a

11.33 ± 1.53a

8.00 ± 0.00a

20.50 ± 0.71b

S. aureus

10.00 ± 0.00a

10.00 ± 0.58a

10.50 ± 0.71a

20.50 ± 2.12b

Note. Values are presented as mean ± standard deviation of three replicates. The mean in the same row with different superscript is significant at p<0.05.

 

 

Table 4 presents the MIC values of propolis extracts, ranging from 390.63 to 1562.50μg/mL. Notably, G. thoracica propolis extract exhibited the lowest MIC value of 390.63μg/mL against B. cereus and M. luteus. H. itama propolis extract showed MIC value of 1562.50 μg/mL against all tested bacteria, whereas T. apicalis propolis extract exhibited MICs of 781.25μg/mL against M. luteus and 1562.50 against B. cereus, S. mutans and S. aureus.

 

 

 

Table 4: The minimum inhibitory concentration (MIC) of ethanolic propolis extracts against selected Gram-positive bacteria.

Bacteria

Minimum inhibitory concentration (μg/mL)

H. itama

G. thoracica

T. apicalis

Ciproflaxin

B. cereus

1562.50 ±0.00

390.63± 0.00

1562.50 ±0.00

0.25±

0.00

M. luteus

1562.50 ±0.00

390.63± 0.00

781.25± 0.00

8.00±

0.00

S. mutans

1562.50 ±0.00

1562.50± 0.00

1562.50 ±0.00

0.25±

0.00

S. aureus

1562.50 ±0.00

1562.50± 0.00

1562.50 ±0.00

1.00±

0.00

Note. Values are expressed as mean ± standard deviation of three replicates.

 

 

 

 

Table 5: The minimum bactericidal concentration (MBC) of ethanolic propolis extracts against selected Gram-positive bacteria.

Bacteria

Minimum bactericidal concentration (μg/mL)

H. itama

G. thoracica

T. apicalis

Ciproflaxin

B. cereus

3125.00 ± 0.00

390.63 ± 0.00

3125.00 ± 0.00

0.25 ±

0.00

M. luteus

3125.00 ± 0.00

781.25 ± 0.00

1562.50 ± 0.00

8.00 ±

0.00

S. mutans

3125.00 ± 0.00

3125.00 ± 0.00

3125.00 ± 0.00

2.00 ±

0.00

S. aureus

3125.00 ± 0.00

3125.00 ± 0.00

3125.00 ± 0.00

1.00 ±

0.00

Note. Values are expressed as mean ± standard deviation of three replicates.

 

 


 

Table 6: Pearson’s correlation coefficients between resin content, TPC, TFC and antibacterial inhibition zone of propolis samples.

Variables

Resin

TPC

TFC

B. cereus

M. luteus

S. mutans

S. aureus

Resin

1

0.903*

0.402

0.836*

0.853*

0.788*

0.771*

TPC

0.903*

1

0.443

0.892*

0.933*

0.851*

0.835*

TFC

0.402

0.443

1

0.434

0.466

0.401

0.398

*Correlation is significant at p<0.05.

 


Based on the results presented in Table 5, it was observed that H itama propolis extract exhibited bacteriostatic activity against all tested bacteria with an MBC value of 3125μg/mL. Additionally, T. apicalis propolis extract also displayed bacteriostatic activity against B. cereus (3125μg/mL), M. luteus (1562.50 μg/mL), S. mutans (3125μg/mL) and S. aureus (3125 μg/mL). On the other hand, G. thoracica propolis extract exhibited bactericidal activity against B. cereus with an MBC value of 390.63μg/mL, in addition to its bactericidal activity against M. luteus (781.25μg/mL), S. mutans (3125μg/mL) and S. aureus (3125μg/mL).

 

In Table 6, the values of Pearson’s correlation coefficient display the strength and association between the resin content, TPC and TFC of propolis and the inhibition zone for all Gram-positive bacteria.  A strong correlation (R2 = 0.903) was observed between the resin content and phenolic content for propolis samples. The resin content also showed a strong correlation with all antibacterial inhibition zones. Similarly, the correlation coefficient shows a strong positive correlation between TPC and the antibacterial inhibition zones.

 

DISCUSSION:

Propolis has garnered attention as a promising alternative therapeutic agent in the fight against bacterial infections28. It has been proven to be useful in treating bacterial pathogens responsible for various ailments, including skin infections, respiratory tract infections, and dental caries29. Notably, the diverse geographic location, bee species, and botanical origin contribute to the variation in the composition and physicochemical characteristics of propolis, ultimately influencing its antibacterial potential8,30,31. This study revealed significant variations in the physicochemical compositions of propolis samples from different stingless bee species inhabiting the same environment and ecological settings. In particular, G. thoracica propolis exhibited notably lower lipid and wax contents but significantly higher resin content compared to H. itama and T. apicalis propolis. Propolis is typically made up of 50% plant resin, 30% beeswax, 10% aromatic oils, 5% pollen, and 5% other organic and inorganic components19. Stingless bees utilize plant resins as a vital component in nest construction and to prevent the growth of bacteria and fungi20. Different species of stingless bee demonstrates distinct foraging behaviours that influence the composition of resins they obtain32. Diverse resin profiles are produced by stingless bee species due to variations in their foraging range, flight distance, and preferred plant sources33,34. In terms of moisture content, this study found it to be greater than previously reported values in Moroccan propolis (1.02-3.65%)35 and Portuguese propolis (3.4-5.4%)36. However, the results of this study are comparable with Ibrahim et al. (2016)37, who demonstrated that the moisture content of stingless bee propolis ranged from 9.90 to 23.72%. Stingless bees are predominantly found in the tropical and subtropical regions of the world, including Malaysia2,5. Malaysia is renowned for its abundant rainfall and high humidity that could contribute to the higher moisture content of stingless bee propolis. Nevertheless, it is noteworthy that lower moisture content of propolis may aid in preventing fungal, bacterial, or yeast growth during storage38,39. Additionally, the propolis samples in this study had an acidic pH, ranging between 5.07±0.08 to 5.61±0.03, which are less acidic than those obtained in other studies35,39.

 

The determination of total phenolic and flavonoid contents is important as these bioactive compounds represent major polyphenols in propolis40. Polyphenols are a class of secondary metabolites that are widely present in propolis and contribute significantly to its therapeutic properties40,41. In this study, significant variations were observed in the total phenolic and flavonoid contents of propolis obtained from different species of stingless bees. Propolis produced by G. thoracica exhibited the highest total phenolic and flavonoid contents when compared to H. itama and T. apicalis propolis, which align with the findings of Adli et al. (2022)21 and Asem et al. (2019)40. These results highlight the influence of bee species on the chemical compositions of propolis. However, the total phenolic and flavonoid contents of propolis shown in this study were generally lower than the previous reported values, ranging from 100.93 to 2391.0mg/mL GAE for TPC and 8.67 to 299.4mg/mL QE for TFC21,31. Interestingly, in another study, the TPC values were found to be relatively lower, ranging from 1.1 to 116.1mg/mL41. The observed differences in chemical constituents of propolis could be attributed to the complex interplay of various factors, such as geographical origin, harvesting period, bee species, and foraging behaviour of the stingless bees20,42.

 

Various studies have reported the antibacterial properties of propolis against a broad spectrum of microorganisms, with a higher sensitivity observed in Gram-positive bacteria8,30. Present studies revealed that all propolis samples exhibited antibacterial activity against the tested Gram-positive bacteria. Notably, G. thoracica propolis displayed the strongest antibacterial activity, exhibiting bactericidal effects against B. cereus. These findings highlight the species-dependent effect of propolis on its antibacterial properties which are in accordance with Abdullah et al. (2020)31, who demonstrated species-specific variations in antibacterial property of propolis, with H. itama showing better activity against P. aeruginosa, B. subtilis and S. aureus. The observed strong correlation between resin and total phenolic contents, and antibacterial activity suggests that the higher resin content in G. thoracica propolis is a key factor contributing to its elevated total phenolic compounds, resulting in enhanced antibacterial efficacy. Furthermore, as reported by Touzani et al. (2018)43, propolis with high resin and a low wax content tend to have a higher level of active compounds, resulting in enhanced antimicrobial activities. The antibacterial effect of propolis is mainly ascribed to its phenolic compounds such as phenolic acids and flavonoids44. These bioactive compounds have been shown to impair the integrity of the bacterial cell membrane, reduce ATP production, and inhibit DNA gyrase, an enzyme involved in bacterial DNA and RNA synthesis45,46,47.  These actions collectively lead to the inhibition of bacterial viability and contribute to the antimicrobial properties of propolis.

 

CONCLUSION:

Overall, this study highlights the significant impact of bee species on the physicochemical characteristics, phytochemical composition, and biological activity of propolis. The propolis produced by G. thoracica has high resin content and elevated total phenolic and flavonoid constituents, resulting in strong antibacterial activity. The distinct foraging activities of different stingless bee species significantly influence the resin content and, consequently, chemical composition, and antibacterial activity of their respective propolis samples. These findings shed light on the intricate relationship between bee species and propolis properties, offering valuable insights for potential therapeutic applications.

 

CONFLICT OF INTEREST:

The authors declare that there is no conflict of interest.

 

ACKNOWLEDGMENTS:

This research was funded by the Geran Penyelidikan Khas from Universiti Teknologi MARA (UiTM) (Reference number: 600-RMC/GPK 5/3 (172/2020)).

 

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Received on 02.08.2023            Modified on 31.10.2023

Accepted on 04.01.2024           © RJPT All right reserved

Research J. Pharm. and Tech. 2024; 17(3):1021-1028.

DOI: 10.52711/0974-360X.2024.00158