1 Introduction

Dengue (DENV) fever is the most common viral infection transmitted by mosquitos of the Aedes species in humans. It has emerged as a public health threat that requires global attention, particularly in tropical and sub-tropical areas [1]. The incidence and frequency of dengue infection are predicted to increase due to changes in climate, travel, socioeconomic position, commerce, and viral features [2]. According to the World Health Organization (WHO), dengue disease states are classified into three categories: undifferentiated fever, dengue fever (DF) and dengue haemorrhagic fever (DHF) [3]. High temperature, vomiting, backache, discomfort behind the eyes, rash and in severe cases abdominal pain, bleeding, and shock are main symptoms of the DENV infection [4]. Various studies have indicated the decrease in platelet counts in DENV infection [5,6,7]. Dengue fever is a disease with worldwide implications, with significant mortality and morbidity. According to one study, 390 million dengue virus infections occur yearly, with 96 million of these emerging clinically [8]. Another research on the incidence of dengue virus infection predicts that 3.9 billion individuals are at risk of infection with DENV [9].

DENV is divided into four genetically different serotypes (DENV-1 to DENV-4) [10]. The WHO's updated DENV treatment recommendations include two major therapeutic treatment methods: fluid administration and symptom-specific treatment [11]. A vaccine named Dengavaxia was approved in some countries for dengue, although it does not provide protection against all serotypes and benefits across all age groups [12]. Approaches based on drug repurposing are also being tested against DENV. Clinical studies were conducted on already licensed medications such as chloroquine, celgosivir, ribavirin, prednisolone, and lovastatin, however none of them showed promising effectiveness against dengue [13, 14]. Hence, there is no specific treatment for dengue. Due to the absence of effective therapeutic approaches for dengue, interest in alternative therapies, i.e. natural and herbal remedies for the condition, has grown.

Traditional Indian remedies (Carica papaya L. Andrographis paniculata (Burm.f.) Nees, Tinospora cordifolia (Willd.) Miers ex Hook.f. & Thomson and goat milk) are being used in the management of DENV infection. Ahmad et al. [15] have reported the efficacy of Carica papaya leaves aqueous extract in patient suffering from Dengue fever [15]. Dengue is associated with thrombocytopenia, whereas Carica papaya leaves are responsible for the increase in platelet count in dengue patients. Various reports are available in literature which have shown increase in platelet count in dengue patients after treatment with Carica papaya leaves extracts [15,16,17,18]. The exact mechanism is unclear; however, possible mechanism could be its membrane-stabilizing properties [19]. Edwin et al. [20] have reported the anti-dengue potential of andrographolide against the primary dengue vector Aedes aegypti [20]. It could be due to its modulation property of various intracellular signaling pathways like NF-κ B [21]. Jayaseelan et al. [22] have reported the antiviral efficacy of Tinospora cordifolia biofabricate copper oxide nanoparticles (CuO NPs) against the larvae of An. stephensi and Ae. Aegypti [22]. The possible mechanism is its inhibitory effects on the structural and non-structural proteins of DENV [23]. The milk derived exosomes from Cow (CME) and Goat (GME) have also shown antiviral properties against Dengue virus (DENV) using an in-vitro infection system [24]. This might be due to its selenium content which is required for the proper functioning of the immune system. [25]. However, there is still much debate over these Traditional Indian remedies treatment's therapeutic effectiveness. Thus, the main objective of the current study is to find out the exact role of Traditional Indian remedies in the treatment of DENV infection.

2 Materials and methods

The protocol of the study was registered with PROSPERO (The International Prospective Register of Systematic Reviews), registration number: CRD42023478874. The study was conducted according to PRISMA (Preferred Reported Items for Systematic Reviews and Meta-analysis) guidelines.

2.1 Eligibility criteria

All experimental (in-silico, in-vitro, in-vivo and clinical) studies were included related to efficacy of Carica papaya, Andrographis paniculata, Tinospora cordifolia and goat milk in the treatment of DENV infection.

2.2 Data source and study selection

A comprehensive search was conducted in PubMed, and Clinical Trial Registry-India (CTRI) since from inception to September 30, 2023 with the search strategy using PubMed. The following search strategy was used: Papaya OR Carica papaya OR Giloy OR Tinospora cordifolia OR Guduchi OR Amrita OR Jawari OR Kundali OR Dhara OR Gurjo OR heart-leaved moonseed OR Goat milk OR Capra hircus milk OR Andrographis paniculata OR Kalmegh OR King of bitters OR Green chiretta OR Creat AND Dengue OR Dandy fever OR Dengue virus OR DENV OR Breakbone fever.

2.3 Data extraction

GJ and DT extracted the data from the included studies in the DES (Data Extraction Sheet). The columns of DES include: First author's name with year of publication, study design, participants, intervention, animal model, extract dose, route of administration and outcome. The disagreement among the authors were resolved after consultation with third author (AK).

2.4 Risk of bias

The quality assessment of included studies in the meta-analysis was done using the Cochrane Risk of Bias (ROB) tool.

2.5 Statistical analysis

Mean difference with 95% confidence interval was calculated using Review Manager version 5.4 software. The selection of model was done based on variations among included studies. I2 statistic was used to quantify heterogeneity among included studies. A funnel plot was used for the qualitative assessment of publication bias.

3 Results

A total of 29,821 studies were found after initial search from PubMed, 6 from CTRI and 20 from other sources. A total of 115 studies were found relevant based on the screening of titles. Out of 115 studies, a total of 104 studies were found relevant based on the abstract. Out of 104 studies, 54 studies were found relevant based on the full texts for qualitative analysis. Finally, 09 studies were found relevant for the quantitative analysis. The selection of studies is presented in Fig. 1.

Fig. 1
figure 1

Selection of studies as per the PRISMA guideline

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3.1 Study characteristics

A total of 54 studies [25 clinical trials, 14 in-vitro findings, 13 in-vivo findings, and remaining 2 in-silico studies] were found relevant for qualitative analysis. All clinical trials (25) and in-vivo studies (13) were related to Carica papaya. In-vitro studies (10) were related to the Andrographis paniculata, and 1 study each related to Tinospora cordifolia and goat milk. The characteristics of included studies are compiled Tables 1, 2, 3, 4, 5, and 6.

Table 1 Characteristics of included RCTs
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Table 2 Characteristics of included in-vitro studies
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Table 3 Characteristics of included in-vivo studies
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Table 4 Characteristics of included in-silico studies
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Table 5 Characteristics of included trials from CTRI
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Table 6 Characteristics of other included studies
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3.2 Risk of bias

The judgements on the risk of bias of included studies for quantitative analysis are summarized in Figs. 2 and 3. Each study was assessed for selection bias, performance bias, detection bias, attrition bias, and reporting bias.

Fig. 2
figure 2

Risk of bias assessment

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Fig. 3
figure 3

Risk of bias summary

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3.3 Efficacy of intervention

3.3.1 Carica papaya

A total of 42 studies were found relevant related with the efficacy of Carica papaya. Out of 42 studies, 9 studies were found relevant for the quantitative analysis. Meta-analysis was performed based on only two evaluation parameters i.e., platelet count and period of hospitalization depending upon the availability of the data.

  1. a)

    Change in platelet count

Five studies having 476 subjects were included for the quantitative analysis. A significant result was observed when Carica papaya was compared with control group [MD = 19.50; 95% CI 1.82–37.18; P = 0.03] as shown in Fig. 4. The heterogeneity among studies was found to be 84% with less publication bias (Figure S1).

Fig. 4
figure 4

Forest plot comparing the mean difference of platelet count between Carica papaya group and control group

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  1. b)

    Period of hospitalization

The overall MD was found to be 1.85; 95% CI 1.41–2.28; P < 0.00001 which indicate significant decrease in period of hospitalization in Carica papaya group as compared to control group (Fig. 5). However, the heterogeneity among studies was found to be high. The funnel plot has also indicated the involvement of publication bias as represented in the Figure S2.

Fig. 5
figure 5

Forest plot comparing the period of hospitalization between Carica papaya group and control group

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3.3.2 Andrographis paniculata

A total of 10 in-vitro studies were found relevant related to the efficacy of Andrographis paniculata in dengue viral infection. The findings of these studies are compiled in Table 1.

3.3.3 Tinospora cordifolia

An in-vitro study related to the antiplasmodial and antilarval efficacy of copper oxide nanoparticles using phytoconstituents of Tinospora Cordifolia leaf extract is included in the SLR. Antiplasmodial efficacy was evaluated against chloroquine-resistant Plasmodium falciparum and antilarval efficacy against Anopheles stephensi (malaria vector) and Aedes aegypti (dengue vector) and compared between synthesized copper oxide nanoparticles (CuO NPs), Tinospora cordifolia leaf extract (TCLE) and copper sulfate (CS) solution. The highest antiplasmodial and antilarval efficacy of copper oxide nanoparticles, Tinospora cordifolia leaf extract and copper sulphate solution was compared and was observed in synthesized copper oxide nanoparticles (CuO NPs) with LC50 values (against Aedes aegypti = 3.69 mg/L, against Anopheles stephensi = 4.06 mg/L) and IC50 for anti-plasmodial efficacy was 19.82 µg/mL [24].

3.3.4 Goat milk

In-vitro study related to the anti-viral activity of goat milk exosomes compared with cow milk exosomes against DENV using cultured Vero cells. First, they infected the Vero cells with DENV-2 and then treated with different concentration of goat milk exosomes (GME) and cow milk exosomes (CME) for 24 and 48 h. A dose dependent inhibition was observed in DENV-2 infection after 48 h when treated with GME compared to this less reduction was observed after 24 h, concluding that GME is more effective in later stages against DENV. CME were found to be less efficient as compared to GME against DENV-2 NS3 expression [24].

4 Discussion

Dengue is currently a threat to about half of the world's population, with 100–400 million cases reported annually [8]. There is no specific treatment for dengue/severe dengue. To best of our knowledge, very few SLR and meta-analysis were conducted so far to find out the role of Traditional Indian remedies in the treatment of dengue. The results of current investigation have shown a significant role of Carica papaya, Andrographis paniculata, Tinospora cordifolia and goat milk in the treatment of dengue. Carica papaya plays a significant role in the treatment of dengue by increasing platelet count [16,17,18]. Charan et al. [26] performed the systematic review and meta-analysis on the efficacy and safety of Carica papaya. Four trials were included in this study, reported the association of Carica papaya leaf extract with increase in platelet count (mean difference [MD] = 20.27 [95% confidence interval (CI) 6.21–34.73; P = 0.005]) and decrease in hospital days (MD = 1.90 [95% CI 1.62–2.18; P < 0.00001]) [26]. In 2019, another systematic review and meta-analysis was conducted by Rajapakse et al. [27], to check the efficacy and safety of Carica papaya. Clinical indications included in this study were recovery in platelet count, period of hospitalization, prevention of plasma leakage, mortality and life-threatening complications. Nine studies were included for SLR and 6 studies were selected for quantitative analysis. This study reported an increase in mean platelet count (mean difference 35.45, 95% confidence interval 23.74–47.15, 129 participants) and also shorten the length of hospital stay (mean difference − 1.98 days, 95% confidence interval − 1.83 to − 2.12, 3 studies, 580 participants). There was no evidence available for other clinical outcomes [27]. Similarly, in our study, we have also observed increase in platelet count in Carica papaya treatment group as compared to control group [MD = 19.50; 95% confidence interval [1.82–37.18]; P = 0.03] and decrease in hospital stay [MD = 1.85; 95% CI (1.41–2.28); P < 0.00001].

The term "heterogeneity" describes the variations in study findings among investigations. Being heterogeneous just means that your data is variable, which is nothing to be afraid about [28, 29]. The findings of this research have also demonstrated the existence of heterogeneity among studies. A funnel plot is typically utilised in order to conduct a qualitative analysis of publication bias, which is yet another essential factor to investigate. The high risk of bias in the included studies can significantly affects the results of the meta-analysis [30, 31]. However, In the current investigation, publication bias assessment is not promising due to availability of a smaller number of studies.

Herbals are not completely safe and found to be associated with various adverse drug reactions [32]. Therefore, the traditional Indian remedies which are included in this study are also might be associated with adverse drug reactions. The most common adverse drug reactions associated with C. papaya are related to gastrointestinal system [19]. The systematic review and meta-analysis was conducted by Worakunphanich et al. [33] to find out the safety profile of Andrographis paniculata and reported most common adverse drug reactions related to gastrointestinal, skin and subcutaneous system [33]. Tinospora cordifolia is also associated with minor ADRs related to the gastrointestinal system [34]. Goat milk is assumed to be safe. However, brucellosis is common in the tropical and sub-tropical regions. Therefore, goat milk should be boiled before use in the Dengue patients.

Herbals are mostly shown their action through inhibition/activation of multiple targets due to their multi-component composition. The possible mechanism of Carica papaya is to increase the platelet counts in Dengue patients through inhibition of heat-induced and hypotonicity-induced hemolysis of erythrocytes. Overall, exact mechanism is unclear so far, however it is likely to possess membrane-stabilizing properties and protect blood cells against stress-induced destruction in Dengue [19]. Further, the exact mechanism of Andrographis paniculata in Dengue is also unclear, however, existing data indicated that the bioactive compounds which are present in Andrographis paniculata like andrographolide could modulates many molecular and cellular mechanisms including oxidative stress, autophagy, mitochondrial function, unfolded protein response pathway etc. to produce anti-viral responses [21]. The antiviral effect of Tinospora cordifolia against Dengue infection might be due to its ability to suppress cytokine storm as well as ability to inhibit the structural and non-structural proteins of Dengue virus [23]. It has been observed that the level of selenium which play an important role in the functioning of immune system is reduced in Dengue infection. The possible mechanism of goat milk in Dengue infection is to increase the level of selenium which will help in proper functioning of the immune system [25]. Overall, Andrographis paniculata, Tinospora cordifolia and goat milk have also potential against DENV infection through multimodal mechanism as indicated by experimental studies, however, clinical studies are limited. Therefore, more well designed randomized clinical trials are required to confirm their exact role in DENV infection.

5 Limitations

The study has the following limitations. The present study is limited by search for relevant articles on limited search engines and the articles published in languages other than English were not considered. Further, subgroup analysis was not done due to limited number of studies.

6 Conclusion

Carica papaya, Andrographis paniculata, Tinospora cordifolia and goat milk have potential against DENV infections, however, more clinical studies are required to confirm the exact role of Andrographis paniculata, Tinospora cordifolia and goat milk.