Bioactive Secondary Metabolites , Antimicobials , Microalgal Toxins, Allelochemicals , Microalgal source of Bioactive compounds ,Modes of Action ,Mechanism of action ,

2. Introduction
 Secondary metabolites are bioactive organic compounds
from microalgae that kill or inhibit the growth of
microorganism.
 Bioactive compounds are natural products which also show
antimicrobial activity against multidrug resistant pathogenic
bacteria.
 Cyanobacteria produce more than 1100 bioactive
metabolites/compouds with diverse biological activities such
as antibacterial, antifungal , anticancer and antiviral activity .

3. Microalgae as source of bioactive metabolites
Organism Bioactive compounds
Chlorella vulgaris Chlorellin
Fischerella muscicola Fischerellin A
Fischerella sp. 12-epi-hapalindole-E
Calothrix sp. Calothrixine A
Scytonema hofmanii Cyanobacterin
Nostoc spongiaeforme Nostocine A
Haematococcus pluvialis Butanoic acid and methyl lactate
Navicula directa Polysaccharide
Dunaliella Primolecta Pheophorbide –alpha-beta like
compounds
Skletonema primolecta Fatty acids and lipids

4.  l
Agar well Diffusion Assay
Test microorganis
Microalgal Extract
Zone of inhibition

5. Microalgae showing Biological activity
 ANTIBACTERIAL ACTION-: Chlorella vulgaris,
Chlamydomonas reinhardtii, Skeletonema costatum,
Haemtococus pluvialis
 ANTIFUNGAL ACTION: Chlamydomonas reinhardtii , Chlorella
pyrenoidosa and Scenedesmus quadricauda. Haematococcus pluvialis
 ANTIVIRAL ACTION: Navicula directa , Dunaliella primolecta
 ANTIMICROALGAL ACTION-: Peridinium bipes , Isochrysis
galbana
 ANTICANCER ACTION : Synecchocystis sp.

6. Antibacterial Action
Microalgae active compounds Target microorganism
Chlamydomonas reinhardtii
Chlorella vulgaris
Methanolic and hexanolic extracts Staphylococcus aureus Staphylococcus
epidermidis Bacillus subtilis , E. coli
Salmonella typhi
Skletonema costatum Long fatty chains of saturated and
unsaturated fatty acids
Vibrio sp.
Haematococcus pluvialis Butanoic acid and methyl lactate Escherichia coli
Staphylococcus aureus
Microalga source Active compound Target microorganism
Chlamydomonas reinhardtii ,Chlorella
vulgaris
Methanolic extracts Candida kefyr ,Candida albicans ,
Aspergillus niger , A. fumigatus
Haematococcus pluvialis Pressurised liquid extract (Butanoic acid and
Methyl lactate )
Candida albicans
Chlorella pyrenoidosa , Scenedesmus
quadricauda
Methanolic/Hexanolic extracts A. niger , A. flavus , Helminthosporium sp.
, Alternaria brassicae ,Candida albicans
,Sacchromyces cerevisiae, Fusarium
moniliforme ,Penicillium herquei
Antifungal activity

7. Antiviral action
Microalga Active compound Target virus
Navicula directa Polysaccharide HSV1 & HSV2 ,Influenza A virus
Dunaliella primolecta Pheophorbide-alpha-beta like
compounds
HSV1
Gyrodinium impudicum Sulfated exopolysaccharide Encephalomyocarditis virus ( EMCV )
Microalga source Active compounds Target microorganism
Peridinium bipes Aquous/water –soluble extract Microcystis aeruginosa
Isochrysis galbana C22H38O7 from cell free filtrates Dunaliella salina , Nitzschia closterium
,Chaetoceros muelleri ,Chlorella
vulgaris , C. gracilis , Platymonas
elliptica
Antimicroalgal action

8. Mode of action
1. Inhibition of photosynthesis:
Eg. Scytonema hofmanii- Cyanobacterin
Fischerella muscicola- Fischerellin A
2 Cellular paralysis:
Eg. Anabaena flos-aquae- causes faster settling of Chlamydomonas reinhardtii
3 Inhibition of nucleic acid synthesis:
Eg-Fischerella sp. (12 – epi-hapalindole E),
Calothrix sp. (Calothrixine A)
4 ROS generation:
Eg. Nostoc spongiaeforme (Nostocine A )
ROS formation in Chlamydomonas reinhardtii

9. CONCLUSION
 Microalgae is rich source of several bioactive
metabolites
 These Bioactive compounds have wide range of
biological activities viz. antibacterial, antiviral,
antifungal and anticancer
 Novel bioactive compounds may be extracted from
microalgae to target multi-drug resistant bacterial and
viral pathogens which cause serious human diseases.
 Anticancer secondary metabolites from microalgae
including cyanobacteria have also been reported.
 There is tremendous possibility of development of novel
drugs from microalgae including cyanobacteria.