Hydro-distilled volatile oils from the leaves of Ocimum gratissimum L. (Lamiaceae)
from 13 populations of different silvicultural zones were evaluated for antimicrobial
activity against Gram positive (Staphylococcus aureus, Bacillus spp.) and Gram
negative (Escherichia coli, Pseudomonas aeruginosa, Samonella typhi, Klebsiella
pneumoniae, Proteus mirabilis) bacteria and a pathogenic fungus Candida albicans. All
the essential oils were active to the tested microbials with different strength. The highest
antimicrobial activity against Gram positive bacteria (Staphylococcus aureus) and Gram
negative bacteria (Pseudomonas aeruginosae and Proteus mirabilis) was observed from
the eastern Kenya (Meru) oil. Meru oil was overall the best and its effectiveness was
consistent on nearly all the microbes tested. The oil from the plant growing in the coastal
region of Kenya (Mombasa) showed the best effect only on Gram negative bacteria
(Escherichia coli and Proteus mirabilis). Both oils (Meru and Mombasa) were
dominated by monoterpenes accounting for 92.48 % and 81.37 % respectively. The
monoterpene fraction was characterized by a high percentage of eugenol (68.8 %) for
Meru oil and 74.10 % for Mombasa oil. The other major monoterpene was methyl
eugenol (13.21 %). Camphor (0.95 %) was observed only in the Meru oil. (Cis)-
Ocimene, (trans)-ocimene and β-pinene were present in both Meru and Mombasa oils.
The sesquiterpenes present in fairly good amounts in both oils were germacrene D and
xxvi
(trans)-caryophyllene. The minor sesquiterpenes were α-farnesene (0.85 %) and β-
bisabolene (0.74 %) which were present in the Meru oil only.
After establishing the best storage conditions and genomic DNA extraction protocol for
O. gratissimum L. which was the detergent SDS and the reducing agent dithiothreitol;
genetic diversity studies involving twelve populations were perfomed using the
amplified fragment length polymorphic (AFLP) markers. Six thousand, two hundred and
thirty seven different AFLP bands were generated by the seven primers used. The total
number of bands scored per primer ranged from 595 (ACT-CTG) to 1335 (ACT-CAA),
with an average of 891 bands per primer. The size of the amplified fragments ranged
from 50 to 472 base pairs (bp).
Estimates of Nei’s unbiased genetic diversity showed some populations with similar
gene diversity (Mill house II and Njoro with H = 0.13; Savona isle, Riat, Chesigei and
Mariakani with H = 0.15; Kibarani and Roret with H = 0.10). Kibarani and Roret were
the least diverse (H = 0.10) and Kiganjo as the most diverse (H = 0.19). The results
showed some great variation in the levels of genetic diversity as also shown by
Shannon’s information index (I). There was some percentage polymorphic loci
correspondence with the diversity estimates. In most cases, populations with high
diversity estimate also showed high percentage polymorphic loci. The genetic variation
was within populations as opposed to among populations. There was small genetic
differentiation in the populations. The FST was zero.
Hydro-distilled volatile oils from the leaves of Ocimum gratissimum L. (Lamiaceae)
from 13 populations of different silvicultural zones were evaluated for antimicrobial
activity against Gram positive (Staphylococcus aureus, Bacillus spp.) and Gram
negative (Escherichia coli, Pseudomonas aeruginosa, Samonella typhi, Klebsiella
pneumoniae, Proteus mirabilis) bacteria and a pathogenic fungus Candida albicans. All
the essential oils were active to the tested microbials with different strength. The highest
antimicrobial activity against Gram positive bacteria (Staphylococcus aureus) and Gram
negative bacteria (Pseudomonas aeruginosae and Proteus mirabilis) was observed from
the eastern Kenya (Meru) oil. Meru oil was overall the best and its effectiveness was
consistent on nearly all the microbes tested. The oil from the plant growing in the coastal
region of Kenya (Mombasa) showed the best effect only on Gram negative bacteria
(Escherichia coli and Proteus mirabilis). Both oils (Meru and Mombasa) were
dominated by monoterpenes accounting for 92.48 % and 81.37 % respectively. The
monoterpene fraction was characterized by a high percentage of eugenol (68.8 %) for
Meru oil and 74.10 % for Mombasa oil. The other major monoterpene was methyl
eugenol (13.21 %). Camphor (0.95 %) was observed only in the Meru oil. (Cis)-
Ocimene, (trans)-ocimene and β-pinene were present in both Meru and Mombasa oils.
The sesquiterpenes present in fairly good amounts in both oils were germacrene D and
xxvi
(trans)-caryophyllene. The minor sesquiterpenes were α-farnesene (0.85 %) and β-
bisabolene (0.74 %) which were present in the Meru oil only.
After establishing the best storage conditions and genomic DNA extraction protocol for
O. gratissimum L. which was the detergent SDS and the reducing agent dithiothreitol;
genetic diversity studies involving twelve populations were perfomed using the
amplified fragment length polymorphic (AFLP) markers. Six thousand, two hundred and
thirty seven different AFLP bands were generated by the seven primers used. The total
number of bands scored per primer ranged from 595 (ACT-CTG) to 1335 (ACT-CAA),
with an average of 891 bands per primer. The size of the amplified fragments ranged
from 50 to 472 base pairs (bp).
Estimates of Nei’s unbiased genetic diversity showed some populations with similar
gene diversity (Mill house II and Njoro with H = 0.13; Savona isle, Riat, Chesigei and
Mariakani with H = 0.15; Kibarani and Roret with H = 0.10). Kibarani and Roret were
the least diverse (H = 0.10) and Kiganjo as the most diverse (H = 0.19). The results
showed some great variation in the levels of genetic diversity as also shown by
Shannon’s information index (I). There was some percentage polymorphic loci
correspondence with the diversity estimates. In most cases, populations with high
diversity estimate also showed high percentage polymorphic loci. The genetic variation
was within populations as opposed to among populations. There was small genetic
differentiation in the populations. The FST was zero.
