Influenza is an acute viral infection of the respiratory tract caused by the Alphainfluenzavirus whose subtypes were responsible for historical pandemics. Recently, the coronavirus SARS-CoV-2 has also affected the world, causing acute respiratory syndrome, thus rendering the search for anti-influenza and anti-SARS-CoV-2 compounds an urgent task. Plants of the genus Siparuna are used in Brazilian folk medicine for treating colds, fever, headaches, and rheumatic pain as well as gastrointestinal disorders. S. apiosyce (“Limão Bravo”) is mentioned in the first Brazilian Pharmacopeia due to its importance as an ingredient in syrup and cough drops. Alkaloids, methylated and glycosylated flavonoids stand out as secondary metabolites described for these species, being also well described in the literature for their antiviral activity. During our investigation of Brazilian plants active against viral infections, the anti-influenza activity of five Amazonian Siparuna (S. cristata, S. decipiens, S. glycycarpa, S. reginae and S. sarmentosa) were investigated, showing the n-butanol extracts of S. glycycarpa and S. sarmentosa as the most active. Dereplication of these extracts pointed alkaloids, O- and C-glycosylated flavonoids as well as dihydrochalcones and a procyanidin dimer as potential active metabolites. On the other hand, the dichloromethane extract from S. cristata containing methylated flavonoids was able to inhibit the in vitro replication of SARS-CoV-2, where it was shown that retusin and kumatakenin presented a higher selectivity index than lopinavir/ritonavir and chloroquine controls. Further in-silico studies showed the potential interaction between these flavonoids and the virus proteases 3CLpro and PLpro. Here we highlight the possible application of compounds isolated from Siparuna species as antiviral agents. 

Infectious diseases caused by pathogens and food poisoning induced by spoilage bacteria pose a global hazard to human health. Microbial resistance has harmed the efficacy of various antimicrobial drugs, which are now used to extend the shelf life, raise the safety of food products in the food business, and suppress diseasecausing germs in medicine. As a result, new antimicrobial agents that can overcome resistance must be developed. Many spices, including clove, oregano, thyme, cinnamon, and cumin, were found to have significant antibacterial and antifungal activity against food spoilage bacteria like Bacillus subtilis and Pseudomonas fluorescens, pathogens like Staphylococcus aureus and Vibrio parahaemolyticus, harmful fungi like Aspergillus flavus, and even antibiotic-resistant microorganisms like methicillin. In addition to their flavor and aroma features, many spices and herbs used today are recognized for their antimicrobial and therapeutic properties. Plant extracts from cinnamon, clove, garlic, mustard, onion, and oregano were sensitive to most foodborne bacterial pathogens studied. The essential oil portion of spices and herbs contains many antibacterial chemicals. Antimicrobial compounds in spices were more responsive to Gram-positive bacteria than those in spices were to Gram-negative bacteria. The degree of sensitivity differed depending on the strain and climatic variables. Spices that stimulate acid generation in starting cultures can have a direct effect on the rate of fermentation. Spices contain antimicrobial compounds such as phenols, alcohols, aldehydes, ketones, ethers, and hydrocarbons. In the current chapter, Indian spices and their key antimicrobial components are explored for their antibacterial activity and ways of action.

Herbal medicines have helped to cure illness because the practice has continued for generations. Multiple alkaloids/compounds that occur naturally (as against single extracts) exhibit synergistic action and do not show antidote action. This naturally occurring combination of compounds exhibits antiviral, antibacterial, antiprotozoal, and antioxidant actions. The cases related to viral, protozoal, and bacterial infections were selected. Patients with amoebiasis, e-coli, gastrointestinal infection, skin and urinary tract infections were treated using herbal drugs. Diagnoses were confirmed with investigations. Repeated investigations were carried out to confirm the improvement.

Most herbal medicines do not exhibit serious side effects and are safe to prescribe, showing greater acceptability. Thus, due to their cost effectiveness, these medicines are in great demand for primary health care for better cultural acceptability and minimal side effects.

Cases varying from COVID 19 to gastrointestinal infection, viral diseases, and skin and wound infections are being treated effectively with herbal drugs.

Infectious diseases are a major cause of morbidity and mortality at a worldwide level. While common cold, encephalitis, meningitis and gastroenteritis are mostly triggered by viruses, cholera, diphtheria, dysentery, tuberculosis, typhoid and pneumonia infections are caused by various bacteria, whereas valley fever, histoplasmosis, candidiasis, ringworm and eye infections are generated by several fungi. Also, ectoparasites like mites, lice, ticks and fleas can be responsible for some infections by attaching to the skin. However, after the onset of COVID-19, which mostly presents as a respiratory disease, a top interest has been put on virus research. Many studies have shown that phytochemicals exert a plethora of biological effects, among them, their antimicrobial action through different mechanisms has been highly underlined. Indeed, they are able to damage the bacterial cell membrane and suppress diverse virulence factors, including inhibition of the activity of various enzymes and toxins and biofilm formation. This chapter summarizes the impact of certain phytochemicals, for example, flavonoids, polyphenols, saponins, steroids, tannins, terpenoids, and alkaloids, as naturally-occurring bioactive compounds present in plants, in several infectious diseases.

Some herbal medicines containing flavonoids form complexes with cell walls of bacteria, protein and extracellular components and are important and effective antimicrobial compounds. Herbal medicines contain terpenoids involved in weakening microorganism cell wall and membranous tissue dissolution, thus inhibiting the growth of infections. Saponins found in herbal medicines cause microbes enzyme leakage from the cell, whereas Steroid in antimicrobial drugs is responsible for liposome leakage from the lipid bilayer membrane. Based on the evidences, the antimicrobial activity of the medicinal plant Veronica biloba was found against E.coli, S.aureus, and Aspergillus fumigatus pathogens. The common herbs tarragon and thyme both contain caffeic acid, which is effective against viruses, bacteria, and fungi. Organosulphur compounds such as allicin, isothiocynate and ajoene have shown antibacterial activity against both gram-positive and gram-negative bacteria. Catechins, the most reduced form of the C3 unit in flavonoid compounds, deserve special mention due to their occurrence in green teas. It was noticed that teas also exerted antimicrobial activity against Vibrio cholerae, S. mutans, shigella and other microorganisms. This chapter focuses on all aspects of infectious diseases and herbal medicines, including chemical constituents and their therapeutic effects. 

Rheumatoid arthritis is a chronic autoimmune disease that affects the small joints of the feet and hands, causing polyarticular inflammation. Uncontrolled synovial tissue is the most prominent symptom of this disease. If left untreated, it can result in significant impairment, adversely impacting the patient's quality of life and elevating death risk. Genetic, environmental, and epigenetic variables are all important in the etiology of this disease. The risk of developing rheumatoid arthritis is not age-related, people over the age of 40, particularly women, are significantly more likely to get the disease than men. There are a variety of therapies that are provided based on the severity of the ailment. However, all of these therapeutic techniques have negative effects as well as significant prices. More than 80% of the population in the world is now believed to use medicinal plants to maintain their health. Plants are the most abundant source of antimicrobial agents, and extracts of numerous edible plant species, herbs, and spices have long been used to preserve food due to the presence of potentially powerful antibacterial components. Not only minerals and primary metabolites are found in medicinal plants, but also a wide range of possible chemical compounds that aid in the adsorption and neutralization of free radicals. Some of the plants that show antioxidant and anti-inflammatory properties against rheumatoid arthritis are discussed in this chapter.